Refine function names and type signatures (#886)

* First name consistency pass. More to come!

* Remove multitouch variable (hopefully this compiles!)

* Remove CreationError::NotSupported

* Add new error handling types

* Remove `get_` prefix from getters.

This is as per the Rust naming conventions recommended in
https://rust-lang-nursery.github.io/api-guidelines/naming.html#getter-names-follow-rust-convention-c-getter

* Make changes to Window position and size function signatures

* Remove CreationError in favor of OsError

* Begin updating iOS backend

* Change MonitorHandle::outer_position to just position

* Fix build on Windows and Linux

* Add Display and Error implementations to Error types

* Attempt to fix iOS build.

I can't actually check that this works since I can't cross-compile to
iOS on a Windows machine (thanks apple :/) but this should be one of
several commits to get it working.

* Attempt to fix iOS errors, and muck up Travis to make debugging easier

* More iOS fixins

* Add Debug and Display impls to OsError

* Fix Display impl

* Fix unused code warnings and travis

* Rename set_ime_spot to set_ime_position

* Add CHANGELOG entry

* Rename set_cursor to set_cursor_icon and MouseCursor to CursorIcon

* Organize Window functions into multiple, categorized impls

* Improve clarity of function ordering and docs in EventLoop

src/platform/ios.rs

@@ -9,12 +9,12 @@ use window::{Window, WindowBuilder};
 /// Additional methods on `EventLoop` that are specific to iOS.
 pub trait EventLoopExtIOS {
     /// Returns the idiom (phone/tablet/tv/etc) for the current device.
-    fn get_idiom(&self) -> Idiom;
+    fn idiom(&self) -> Idiom;
 }
 
 impl<T: 'static> EventLoopExtIOS for EventLoop<T> {
-    fn get_idiom(&self) -> Idiom {
-        self.event_loop.get_idiom()
+    fn idiom(&self) -> Idiom {
+        self.event_loop.idiom()
     }
 }
 
@@ -23,43 +23,43 @@ pub trait WindowExtIOS {
     /// Returns a pointer to the `UIWindow` that is used by this window.
     ///
     /// The pointer will become invalid when the `Window` is destroyed.
-    fn get_uiwindow(&self) -> *mut c_void;
+    fn ui_window(&self) -> *mut c_void;
 
     /// Returns a pointer to the `UIViewController` that is used by this window.
     ///
     /// The pointer will become invalid when the `Window` is destroyed.
-    fn get_uiviewcontroller(&self) -> *mut c_void;
+    fn ui_view_controller(&self) -> *mut c_void;
 
     /// Returns a pointer to the `UIView` that is used by this window.
     ///
     /// The pointer will become invalid when the `Window` is destroyed.
-    fn get_uiview(&self) -> *mut c_void;
+    fn ui_view(&self) -> *mut c_void;
 
     /// Sets the HiDpi factor used by this window.
-    /// 
+    ///
     /// This translates to `-[UIWindow setContentScaleFactor:hidpi_factor]`.
     fn set_hidpi_factor(&self, hidpi_factor: f64);
 
     /// Sets the valid orientations for screens showing this `Window`.
-    /// 
+    ///
     /// On iPhones and iPods upside down portrait is never enabled.
     fn set_valid_orientations(&self, valid_orientations: ValidOrientations);
 }
 
 impl WindowExtIOS for Window {
     #[inline]
-    fn get_uiwindow(&self) -> *mut c_void {
-        self.window.get_uiwindow() as _
+    fn ui_window(&self) -> *mut c_void {
+        self.window.ui_window() as _
     }
 
     #[inline]
-    fn get_uiviewcontroller(&self) -> *mut c_void {
-        self.window.get_uiviewcontroller() as _
+    fn ui_view_controller(&self) -> *mut c_void {
+        self.window.ui_view_controller() as _
     }
 
     #[inline]
-    fn get_uiview(&self) -> *mut c_void {
-        self.window.get_uiview() as _
+    fn ui_view(&self) -> *mut c_void {
+        self.window.ui_view() as _
     }
 
     #[inline]
@@ -79,13 +79,13 @@ pub trait WindowBuilderExtIOS {
     ///
     /// The class will be initialized by calling `[root_view initWithFrame:CGRect]`
     fn with_root_view_class(self, root_view_class: *const c_void) -> WindowBuilder;
-    
+
     /// Sets the `contentScaleFactor` of the underlying `UIWindow` to `hidpi_factor`.
-    /// 
+    ///
     /// The default value is device dependent, and it's recommended GLES or Metal applications set
-    /// this to `MonitorHandle::get_hidpi_factor()`.
+    /// this to `MonitorHandle::hidpi_factor()`.
     fn with_hidpi_factor(self, hidpi_factor: f64) -> WindowBuilder;
-    
+
     /// Sets the valid orientations for the `Window`.
     fn with_valid_orientations(self, valid_orientations: ValidOrientations) -> WindowBuilder;
 }
@@ -113,13 +113,13 @@ impl WindowBuilderExtIOS for WindowBuilder {
 /// Additional methods on `MonitorHandle` that are specific to iOS.
 pub trait MonitorHandleExtIOS {
     /// Returns a pointer to the `UIScreen` that is used by this monitor.
-    fn get_uiscreen(&self) -> *mut c_void;
+    fn ui_screen(&self) -> *mut c_void;
 }
 
 impl MonitorHandleExtIOS for MonitorHandle {
     #[inline]
-    fn get_uiscreen(&self) -> *mut c_void {
-        self.inner.get_uiscreen() as _
+    fn ui_screen(&self) -> *mut c_void {
+        self.inner.ui_screen() as _
     }
 }
 
@@ -130,7 +130,7 @@ pub enum ValidOrientations {
     LandscapeAndPortrait,
 
     Landscape,
-    
+
     /// Excludes `PortraitUpsideDown` on iphone
     Portrait,
 }
@@ -143,7 +143,7 @@ impl Default for ValidOrientations {
 }
 
 /// The device [idiom].
-/// 
+///
 /// [idiom]: https://developer.apple.com/documentation/uikit/uidevice/1620037-userinterfaceidiom?language=objc
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum Idiom {