Add ordered_by_name scope to WorldLocation

Sorts worldlocations by name using the I18n.defualt_locale translations regardless of the current I18n.locale.  Wherever we were just using .all or doing a manual .sort_by(&:name) we now use this scope.
Make WorldLocation.all_by_type order by name within each type group

Note: this mixes sql(order) and enumerable(group_by) and I'm relying on group_by to maintain the order returned by the sql.  There's a test though, just in case.
Add existing UI for filtering by location to Publications index
Allow setting of important board member count
Show important board members with photos

Each important board member should have their photo showing. Updated the
views to work with this.

Also renamed the `civil_servant` variable to `board_members` as it is
more consistent with how we refer to them in other parts of the project.
Style the button consistently.
Merge pull request #230 from alphagov/important-board-members

Important board members
Merge pull request #231 from alphagov/allow-filtering-publications-by-location

Allow filtering publications by location, and ordering by name