Merge pull request #1989 from DavidOliver/integration

Set white background for inputs and multiple selects
Merged Publish Filtering into adminsistrationpage class
Remove reference to JS and CSS in createInterface function
Moved filtering to contentPublish class
temp added js and css for testing
removed debug log
Rename and move files
First steps to integrate Publish Filtering assets into the core
Variable names
Simplify styles
Update assets
Move filtering initialisation to backend.views.js
Add AJAX page to fetch filters
Load filter options asynchronously
Remove incompatible fields from content page
Revert "Remove incompatible fields from content page"

This reverts commit dfcfba0f76f07c016cd536e1641bf414cac954a4.
Remove array of incompatible publish filter fields, in place of new method
Slight simplifications
Make sure "Add button" is appended correctly
Fix gradients