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_impl/macos/monitor.rs

@@ -9,7 +9,7 @@ use platform_impl::platform::util::IdRef;
 #[derive(Clone, PartialEq)]
 pub struct MonitorHandle(CGDirectDisplayID);
 
-pub fn get_available_monitors() -> VecDeque<MonitorHandle> {
+pub fn available_monitors() -> VecDeque<MonitorHandle> {
     if let Ok(displays) = CGDisplay::active_displays() {
         let mut monitors = VecDeque::with_capacity(displays.len());
         for display in displays {
@@ -21,7 +21,7 @@ pub fn get_available_monitors() -> VecDeque<MonitorHandle> {
     }
 }
 
-pub fn get_primary_monitor() -> MonitorHandle {
+pub fn primary_monitor() -> MonitorHandle {
     MonitorHandle(CGDisplay::main().id)
 }
 
@@ -38,11 +38,11 @@ impl fmt::Debug for MonitorHandle {
         }
 
         let monitor_id_proxy = MonitorHandle {
-            name: self.get_name(),
-            native_identifier: self.get_native_identifier(),
-            dimensions: self.get_dimensions(),
-            position: self.get_position(),
-            hidpi_factor: self.get_hidpi_factor(),
+            name: self.name(),
+            native_identifier: self.native_identifier(),
+            dimensions: self.dimensions(),
+            position: self.position(),
+            hidpi_factor: self.hidpi_factor(),
         };
 
         monitor_id_proxy.fmt(f)
@@ -54,48 +54,48 @@ impl MonitorHandle {
         MonitorHandle(id)
     }
 
-    pub fn get_name(&self) -> Option<String> {
+    pub fn name(&self) -> Option<String> {
         let MonitorHandle(display_id) = *self;
         let screen_num = CGDisplay::new(display_id).model_number();
         Some(format!("Monitor #{}", screen_num))
     }
 
     #[inline]
-    pub fn get_native_identifier(&self) -> u32 {
+    pub fn native_identifier(&self) -> u32 {
         self.0
     }
 
-    pub fn get_dimensions(&self) -> PhysicalSize {
+    pub fn dimensions(&self) -> PhysicalSize {
         let MonitorHandle(display_id) = *self;
         let display = CGDisplay::new(display_id);
         let height = display.pixels_high();
         let width = display.pixels_wide();
         PhysicalSize::from_logical(
             (width as f64, height as f64),
-            self.get_hidpi_factor(),
+            self.hidpi_factor(),
         )
     }
 
     #[inline]
-    pub fn get_position(&self) -> PhysicalPosition {
-        let bounds = unsafe { CGDisplayBounds(self.get_native_identifier()) };
+    pub fn position(&self) -> PhysicalPosition {
+        let bounds = unsafe { CGDisplayBounds(self.native_identifier()) };
         PhysicalPosition::from_logical(
             (bounds.origin.x as f64, bounds.origin.y as f64),
-            self.get_hidpi_factor(),
+            self.hidpi_factor(),
         )
     }
 
-    pub fn get_hidpi_factor(&self) -> f64 {
-        let screen = match self.get_nsscreen() {
+    pub fn hidpi_factor(&self) -> f64 {
+        let screen = match self.nsscreen() {
             Some(screen) => screen,
             None => return 1.0, // default to 1.0 when we can't find the screen
         };
         unsafe { NSScreen::backingScaleFactor(screen) as f64 }
     }
 
-    pub(crate) fn get_nsscreen(&self) -> Option<id> {
+    pub(crate) fn nsscreen(&self) -> Option<id> {
         unsafe {
-            let native_id = self.get_native_identifier();
+            let native_id = self.native_identifier();
             let screens = NSScreen::screens(nil);
             let count: NSUInteger = msg_send![screens, count];
             let key = IdRef::new(NSString::alloc(nil).init_str("NSScreenNumber"));