Corrected layout of magnifierInvertColours adjuster.
Made the magnifierInvertColours template and styling reusable as "icon
check adjuster".
Renamed the template of the iconCheckAdjuster and using that for
magnifierInvertColours preference.
Created the showCrossHairs adjuster.
Added the "icomoon" font icons.
Using the "icomoon" font icons in all iconCheckAdjusters.