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
Merge branch 'refactor-offers' into machtfit

* branch refactor-offers:
  Support multiple benefits per line
  Refactor offers
  Remove conditions and benefits

*M https://github.com/tangentlabs/django-oscar/pull/1414
Merge branch 'checkout-refactor' into machtfit

* branch checkout-refactor:
  WIP Refactor checkout

- https://github.com/tangentlabs/django-oscar/pull/1423
Merge branch 'tables-plural-caption' into machtfit

* branch tables-plural-caption:
  Show number of categories in table caption
  Introduce a customizable caption with the number of rows in it
  Derive tables from correct base class to enable customizations
  Move queryset_{description,icon} to Table class
Merge branch 'disable-button-on-submit' into machtfit

* branch disable-button-on-submit:
  disable-on-submit all submit buttons: demo site
  disable-on-submit all submit buttons: sandbox
  disable-on-submit all submit buttons: dashboard
  disable-on-submit all submit buttons: frontend
  Copy disable-on-submit functionality over from frontend to dashboard
  Allow easy overriding of jquery-ui
  Remove jquery copy in jquery-ui
  Update and minimize jquery-ui
  Test for data-loading-text directly
Merge branch 'css-changes' into machtfit

* branch css-changes:
  Undo this bootstrap modification. It makes things harder to read.
  Add CSS to vertically align plain text with the label in a horizontal form
  Undo border color changes that didn't catch all borders
  Reduce whitespace above black bar at the bottom and the form above
  Remove deviations from stock bootstrap that caused problems
  Use more down-to-earth z-index.
  Don't mess with my CSS like this!
  Visually connect tabs with tab content through a well
  Set a bigger font size and more readable font
  Actually use the variables from variables.less
  Remove unused CSS
  Bigger font for inputs
  Leave non-wysiwyg text areas alone
  Use bootstrap button color instead of the same color for all button types
  Don't overwrite bootstrap error, success and information alert colors
  Update less to 1.7.3 and enable source maps
Bump version.