Bring editions filter script inline with style guide
Consolidate admin editions filter into single form
Add 'admin filters docs with javascript' feature
Admin editions filter uses xhr to update results

• Re-writes javascripts/admin/view/editions/index.js do update results over xhr
• Moves search results view into own partial and modifies controller to respond to
xhr requests with that partial.
Added a js proxifier, editions filter uses it

proxifier.js is the important part of this commit.  It's a work
around for the need to endlessly proxy functions when using the
constructor / prototype pattern. See changes to STYLEGUIDE.md for
more details.
Filter doesn't do duplicate requests
Proxifier.proxifyAllMethods is a little less silly
Merge pull request #1169 from alphagov/improve-admin-editions-filter

Improve admin editions filter

[Delivers https://www.pivotaltracker.com/story/show/61476834]