Policy filter to include relevant_to_local_government

Also changed the copy to use document_type_plural
EditionsController adds a default state param of 'active'

This is to avoid selecting 'all' from the filter menu and not having anything selected presenting different results.

For: https://www.pivotaltracker.com/story/show/46734111
EditionsController adds a default world_location_ids param of 'all'

This is so the front end will highlight "All" world locations even if you didn't select one.

For: https://www.pivotaltracker.com/story/show/46734111
Tidy up admin edition filtering UI

1. make sure each filter option that is rendered as a form has hidden fields for the filter options that make sense (state, type, etc..)
2. use the @filter.options instead of params to query values (because we now inject some defaults)
3. highlight the 'world location ids' options if selected
Remove meaningless test for admin edition filter ui
Importing news articles supports attachments
DRY up attachment importing

Move the code that represents the generic behaviour for acquiring
attachments from an import row up to the base class.
Merge pull request #372 from alphagov/local-gov-filter-on-policies

Policy filter to include relevant_to_local_government

https://www.pivotaltracker.com/story/show/46545179
Merge pull request #386 from alphagov/fix_admin_edition_filtering

Fix admin edition filtering

https://www.pivotaltracker.com/story/show/46734111
Merge pull request #387 from alphagov/news-import-attachments

Add attachment support to news article imports

https://www.pivotaltracker.com/story/show/46802351
Clear priorities for the even floated children

Two column layout so every second child should be clearing the float.
Also added some padding for aesthetic reasons.

https://www.pivotaltracker.com/story/show/46617095