Added keyboard events for Tizen

Keyboard events are now fired for KEY_UP and KEY_DOWN events. This gives lime support for handing the 'back' and 'menu' buttons, any device OEM buttons, and external keyboards.

Key mappings for Tizen are defined in this enum: [c++](https://gist.github.com/lpmitchell/352a64cfdf80dfcdea89) or [haxe version](https://gist.github.com/lpmitchell/a7726a22c362efa36cda)