The subsequent pages from admin tab were already refactored :
- Admissions
- Users

The next pages are:
- Invite people
- News

refs #458
Refactored all the pages inside the admin tab in spaces.

I made changes on the styles of the pages, standardized all styles, fixed some incorrect links, transfer the "Join Requests" to a separate controller to organize the code and change the tokenInput in some pages to select2.

Fixes #458
Merged refactoring of spaces admin