Horizon checkboxes were using a standard checkbox. Unfortunately,
this type of checkbox is only customizable through Chrome, and
even then, its not completely flexible.
The default checkboxes have now been altered to allow for a highly
customized experience through the use of CSS pseudo elements and
Icon Fonts. This allows the color, size and unselected and selected
states of the checkbox to be customized.
The 'default' theme uses the standard Font Awesome checked and
unchecked icons. The 'material' now uses the Material Design
checkbox design.
It was also noticed (and fixed) that the help-icon on the forms
were not the same color as its corresponding text.
Partially-Implements: blueprint horizon-theme-css-reorg
Change-Id: I52602357d831a5e978fe6916b37b0cde9edb2b9b
259973dd06