* Initial code to get unifiied image handling
- not yet tested
- still using FileImageSource in some areas
* Updated the button renderers and added tests for Android
* Updated a few more of the Android renderers
- also added an `IsEmpty` property to the ImageSource to indicate if this source actually contains data that can be used to try and load an image
- added a few more "tests"
- includes the changes for #4916
* A few more changes
* Keep the default page for the sample app
* Changing everything to ImageSource and going from there
- Android, iOS, UWP and WPF are compiling
- GTK, Mac and Tizen are not yet finished
- Added a new interface for UWP to return an IconElement in addition to ImageSource (for app bar buttons)
- not tested yet, nor are there any tests
* Renamed the property to be more useful
* All of Android is now async
- still only minimal tests
- also removed the bits that are in https://github.com/xamarin/Xamarin.Forms/pull/4948
* Update Xamarin.Forms.Platform.cs
* A few fixes to whitespace and nameof()
* Updated iOS and UWP wirth async image sources
* A few fixes and WPF support
* A few fixes for Android after the big merge
* Updated a few more loaders:
- ios
- macos
- tizen
- gtk
* Fix a few things after the merge
* - cast type to FileImageSource
* fix setting of title content if icon doesn't load
* fix IButtonLayoutManager to return correct control
* remove cast and add pack api
* - fix timing issues with layout/invalidation
* - remove aggresive element invalidations for now
* first set of api changes
* obsolete old apis and create new ones for ImageSource
* obsolete messages and static ordering fix
* add tests
* switch default on windows to show images on tabs
* - XStatic obsolete fix
* fix NPC test and bring back alert check on uwp
Fixes#3207Fixes#4689
Matthew Leibowitz
E.Z. Hart
E.Z. Hart