Change board/committee pages

Ghost User
2016-10-05T19:32:55+02:00

Closes #69

- Remove JavaScript usage for the board pages and use indexed urls
- Rename the urls of the committee pages
- Add the board url to the menu
- Replace default committtee placeholder image
- Preserve the i18n fields from a base class in the translations util
- Fix adding a CommitteeMembership for a board (they were not shown in the list due to the manager being overridden)
- Fix problems when adding/updating a CommitteeMembership of a user that is marked as chair.
- Translatable committee names
- Translatable roles in committeememberships