Added emulator support for android.

Hi Joshua,
We added support of "openfl test android -simulator" ( it will be usefull for the CI ).
We left some comments in the code to explain the current limitations and the possible improvements.

Some interesting infos : 
Openfl is using OpenGL, therefore the AVD should have "enable GPU" option checked and API Level >15.
On mac, this checkbox isnt here in the AVD Manager, but we force the option when launched from openfl, which means that if a user launch the emulator manually on mac, it wont have OpenGL and the openfl app will display a blank screen and scream "OpenGL ES not implemented".

BTW we think its important to have a collaborative wiki for openFL to add such kind of infos, what do you suggest ?

- team Motion-Twin