res: drawable: Launcher icon for upcoming Android release

Android's new material design emphasizes flat icons.

patchset v2 -
    Improve flat shadow angles
    Create flat shadow for inner circle
    Fix antialiasing font discoloration
    Slight size decrease to better match the old icon

Optimize icons using lossy compression via:
    https://github.com/SyNtheticNightmar3/optimize_png
Total Results:
    Old size: 56521 bytes
    New size: 25364 bytes
    Reduced:  31157 bytes (44.87% of original total size)