Improved the "should render" logic, so rendering occurs at the desired frame rate, even if sleeping results in minor differences in the poll time
Hide status bar text for iOS when fullscreen is true
Getter functions for Tilesheet

Added getTileCenter, getTileRect and getTileUVs to reflect
openfl.display.Tilesheet.
This necessitates adding haxe arrays for tiles, points and uvs, but
adding tiles is rare and overhead is negligible.
Upside is Tilesheets are far less opaque. Downside is users can shoot
themselves in the foot if they want, or data can potentially desync
between nme and openfl.