Bootstrap 3 - Authentication fixes

When only one external strategy is enabled, the "Sign in" links, takes
you straight to the API endpoint.

A couple of small visual fixes are included such as:
 * aligning search icon with "Sign in"
 * proper padding in the sign in drop down
 * dotted border when in small view mode
 * new visual buttons for external strategies

As the external authentication buttons their designs have changed, the
auth-buttons.css file is no longer necessary so it has been removed.

Fixes for #3406 and 3446
Aligned search icon with sign in button
Not showing login popover when the only enabled strategies are cas or shib.
Made the auth buttons for cas and shib skinnable
Merge remote-tracking branch 'simong/bootstrap3-authentication' into bootstrap3-authentication
Follow up on authentication fixes
Merge origin/bootstrap3 and fix conflicts
Merge branch 'bootstrap3' of https://github.com/sakaiproject/3akai-ux into bootstrap3-authentication
Authentication improvements
Merge branch 'bootstrap3-authentication' of https://github.com/bp323/3akai-ux into bootstrap3-authentication
Follow up on authentication issues
Fixed IE9 background-color issue
Merge branch 'bootstrap3' of https://github.com/oaeproject/3akai-ux into bootstrap3