Added lock and unlock icons.
Added mail icon.
Added camera icon.
Added margin to lock / unlock icons.
Added margin to fullscreen icon.
Fixed GIMP edit manual.
Added normal screen icon.
Added finish icon.
Added info icon.
Added template: square.
Added check icon.
Modified finish icon to smaller.
Added done icon.
Added plus icon.
Added star icon.
Added other types of comment: comment2, comment3.
Added arrows.
Added caution icon.
Added left-right and up-down icons.
Updated contributing doc: drawable-xxhdpi -> drawable-xhdpi.