* Fullscreen Modals have been removed
These weren't working properly anyways, and the styling is very
unpleasant: https://i.imgur.com/QfvGli7.png
* Added two more modal sizes: xs and xl, and added all modals sizes
to the theme preview page. Also updated the theme preview page
to use fa-close instead of 'x'.
* Cleaned up Spinner css to use modal sizes properly. Themability
of spinner to come later.
* Confirmation Modal JavaScript was cleaned up, and contents turned
into an easier to digest client side template. Themability of
client side templates show cased in 'material' design.
* 'material' confirmation dialog was altered to show how themes can
make use of overriding client-side templates.
* Moved the Bootstrap helper variables into its own file.
* Added helper variables for various modal calculations.
Change-Id: I599ad2ffcf3034a24a19bc87e6ebed3eab079f45