Test for data-loading-text directly

This reduces API complexity at the cost of removing the possibility to get
the pure bootstrap behaviour that doesn't check for invalid fields. I
cannot imagine a use case where the pure bootstrap behaviour is better, so
I took the opportunity to reduce complexity.
Update and minimize jquery-ui

So that it doesn't unnecessarily conflict with bootstrap's $.fn.button().

This is a jQuery UI custom download with just the components we currently
use:

* Version: 1.11.2
* Interactions
  * Sortable
* Theme: Cupertino

(Other dependencies get selected automatically.)
Remove jquery copy in jquery-ui

We get our jQuery elsewhere.
Allow easy overriding of jquery-ui

In case an oscar implementation needs more components than standard oscar
Copy disable-on-submit functionality over from frontend to dashboard
disable-on-submit all submit buttons: frontend
disable-on-submit all submit buttons: dashboard
disable-on-submit all submit buttons: sandbox
disable-on-submit all submit buttons: demo site
Improve docs for Application.permissions_map

This just led to confusion, so I decided to improve the docs a bit.

We really should be using Pytohn sets instead of lists for this.
Merge pull request #1554 from machtfit/disable-button-on-submit

Disable button on submit
Recompile CSS files

See https://github.com/django-oscar/django-oscar/commit/8e2b12647ba78a749b73c804d5d7c9df52d81afa#commitcomment-8502671
Update less to 1.7.3 and enable source maps

Don't use requirements-less.txt now, instead just use npm to install less.
Don't overwrite bootstrap error, success and information alert colors

http://getbootstrap.com/2.3.2/components.html#alerts

git blame doesn't reveal any useful information as to why this was added in
the first place.
Use bootstrap button color instead of the same color for all button types
Leave non-wysiwyg text areas alone

as was the intention according to the comment above the CSS rule.

Without this regulating the size of the textarea with
attrs={'rows': x, 'cols': y} was not effective.
Bigger font for inputs
Remove unused CSS

There's no category-selected in the Dashboard as far as I can find
Actually use the variables from variables.less
Set a bigger font size and more readable font

The previously used font was too thin.