[CLC-2985] Fix styling of Add User to Course Tool
[CLC-2985] Implemented bCourse color variables, applied to AUC tool button
[CLC-2985] Removed unnecessary 'small-12' class. Renamed center alignment class to be more semantic
[CLC-2985] Converted font-size to pixels. Removed unnecessary float property.
Merge pull request #1933 from redconfetti/CLC-2985-fix-auc-styling

[CLC-2985] Fix styling of Add User to Course Tool