Add OpenGL ES 2.0 to required Android features

OpenGL ES 2.0 is used by default in template, so it should be forced on devices
by adding uses-feature in AndroidManifest.xml:

    <uses-feature android:glEsVersion="0x00020000"/>
Merge pull request #26 from aginiewicz/opengl-es-20-in-manifest

Add OpenGL ES 2.0 to required Android features