Add "e.g." to date filter placeholder
Add "or" to world location filter label

Also a bunch of other minor logic fixes in the filter to make
sure the organisation and world location filters show up when
they should.
Make "all" options visible in admin filters
Add "enter" button when text filters are changed
Add reset link to admin document filter
Add some missing semicolons.
Merge pull request #910 from alphagov/57301376-admin-document-filter-changes

Admin document filter changes

https://www.pivotaltracker.com/story/show/57301376