Course Email bug fixes and improvements

Fixed Canvas API non-documented issue by declaring limit of users
(otherwise, default was to get only 10 users);
Improved responsive CSS for desktop browsers (when not maximized) and
for mobile/tablet viewing;
Moved buttons to right side of page;
Maximized email list box height by setting table height to 100%;
Removed scrollbar as now obsolete;
Moved jQuery empty form warning message to top of page near submit
button;
Set to be left aligned to match style of Canvas pages;
Added html5 wrapper tags;
Added Bootstrap viewport meta tag;
Added groups for UI button categories (Actions, Filters, Notes);
Added stylized colors for UI button categories;
Added jQuery fadeIn and fadeOut transitions for form warning message;