Make core Ticker abstract and public (#116)

* Make core Ticker abstract and public
Make the core Ticker abstract and public so it can be inherited by platform
implementations; remove now-unused parts of original Ticker; add CreateTicker
to IPlatformServices; remove unused CreateTimer methods from IPlatformServices

* Add docs for Ticker

* Remove unnecessary Ticker.Default set

* Move Ticker into Internals

* Update Ticker docs

* Remove old Ticker docs

* Remove commented code

1 files changed, 3 insertions, 22 deletions

diff --git a/Xamarin.Forms.Platform.WP8/WP8PlatformServices.cs b/Xamarin.Forms.Platform.WP8/WP8PlatformServices.cs
index 4d49315e..30623088 100644
--- a/Xamarin.Forms.Platform.WP8/WP8PlatformServices.cs
+++ b/Xamarin.Forms.Platform.WP8/WP8PlatformServices.cs
@@ -9,6 +9,7 @@ using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Threading;
 using Windows.System;
+using Xamarin.Forms.Internals;
 using Xamarin.Forms.Platform.WinPhone;
 
 namespace Xamarin.Forms
@@ -22,29 +23,9 @@ namespace Xamarin.Forms
 			Deployment.Current.Dispatcher.BeginInvoke(action);
 		}
 
-		public ITimer CreateTimer(Action<object> callback)
+		public Ticker CreateTicker()
 		{
-			return new _Timer(new Timer(o => callback(o)));
-		}
-
-		public ITimer CreateTimer(Action<object> callback, object state, int dueTime, int period)
-		{
-			return new _Timer(new Timer(o => callback(o), state, dueTime, period));
-		}
-
-		public ITimer CreateTimer(Action<object> callback, object state, long dueTime, long period)
-		{
-			return new _Timer(new Timer(o => callback(o), state, dueTime, period));
-		}
-
-		public ITimer CreateTimer(Action<object> callback, object state, TimeSpan dueTime, TimeSpan period)
-		{
-			return new _Timer(new Timer(o => callback(o), state, dueTime, period));
-		}
-
-		public ITimer CreateTimer(Action<object> callback, object state, uint dueTime, uint period)
-		{
-			return new _Timer(new Timer(o => callback(o), state, dueTime, period));
+			return new WinPhoneTicker();
 		}
 
 		public Assembly[] GetAssemblies()