Add supersu option [3/3]

Added SuperSu. Taken from omni rom, if supersu is installed it will hide icon from launcher and show this menu, if not this option will be hide automatically
(needs eu.chainfire.supersu package)

Icons are here:
res/drawable-hdpi/ic_settings_supersu.png  --> https://gerrit.omnirom.org/#/c/4932/1/res/drawable/hdpi/ic_settings_supersu.png
res/drawable-hdpi/ic_settings_supersu.png  --> https://gerrit.omnirom.org/#/c/4932/1/res/drawable-hdpi/ic_settings_supersu.png
res/drawable-mdpi/ic_settings_supersu.png -->https://gerrit.omnirom.org/#/c/4932/1/res/drawable-xhdpi/ic_settings_supersu.png