Bitmap tests: Add Clone using Tiles test.
Merge remote-tracking branch 'picoe/develop' into dev3
EtoEnvironment.Platform: Add iOS and Android detection. Fixes picoe/Eto#182.
iOS: Support Retina-compatible bitmap graphics contexts. Fixes picoe/Eto#181.
Fix Generator.Detect to use System.Environment.OSVersion.Platform.
Merge pull request #180 from corliss/dev3

Test case for picoe/Eto#179