closes #6223

Updated Weekly User Stats page to show the most recent week. Page should show most recent information

* thanks to @maxwell for the initial work on this

port admin pages to bootstrap
* improve user view on admin search page
* add 'close account' link to each user in the search results
* keep the same blue color for the admin menu

some refactoring of the routes and the admin code
* try to be more RESTful (possibly)
* use a 'UserSearch' model for search parameters and querying

add changelog entry

  * refactor a bit #weekly_user_stats
  * pass 0 instead of "" to i18n
  * use the first week if none is provided

* Rename and reorganize post fetcher to fix autoloading, also let it use
  Faradays default connection so we get nice redirects
* Add initializer to load libs at a central place
* added lib dir to autoload_once paths to increase thread safety
* Moved lib/exceptions.rb to lib/diaspora/ to conform namespacing

- `Rails.root` is a `Pathname`, so let's use `Rails.root.join`
- Clean up most of the remaining `File.join`s

and improving admin functionality

improved weekly_user_stats in admin with a dropdown box by week to list all new users of that week also a link_to the user profile so the admin can sent welcome msgs, etc

MS DG IZ major invite refactor. all tests are green minus weird stuff on dans computer, need to checkout this out on pivots