Bug 937673 - Modify groups model to allow user-created curated groups

* Add flags for functional area, members_can_leave, visible
* Get rid of system, auto_complete, and related fields
Bug 938184 - Don't allow creating groups while editing user profile

Part of the changes for curated groups is that groups will only be
creatable from the groups list page, so only allow people editing
their profiles to select groups that already exist.

The tag-it library that was being used to implement the groups
selection could not easily be configured or modified to prevent
users from selecting non-existent items, so the groups field
was changed to use django-selectable. Styling was added to make
the django-selectable field look like the current tag-it fields,
which are still being used for e.g. skills and languages.
Remove some unused code from groups/forms.py
[Fix Bug 938674] Added Create Group button the Groups list page (+2 squashed commits)

only translating the words in the create group button

[Fix Bug 938674] Added Create Group button the Groups list page
merging Bug 937673 - Modify groups model to allow user-created curated groups
merging: Bug 938184 - Don't allow creating groups while editing user profile

Part of the changes for curated groups is that groups will only be
creatable from the groups list page, so only allow people editing
their profiles to select groups that already exist.

The tag-it library that was being used to implement the groups
selection could not easily be configured or modified to prevent
users from selecting non-existent items, so the groups field
was changed to use django-selectable. Styling was added to make
the django-selectable field look like the current tag-it fields,
which are still being used for e.g. skills and languages.
merging:  Remove some unused code from groups/forms.py
Merge remote-tracking branch 'upstream/pr/726' into curatedgroups-merge
Update migrations
Merge pull request #1 from dpoirier/curatedgroups-merge

Update migrations for curatedgroups-merge
Fix group editing
Merge pull request #2 from dpoirier/fix-group-editing

Fix group editing
Merge branch 'curatedgroups-merge' into curatedgroups
Merge remote-tracking branch 'mozilla/master' into curatedgroups

Conflicts:
	mozillians/settings/base.py
	mozillians/templates/phonebook/edit_profile.html
[Fix Bug 916806, Fix Bug 950229] Add external accounts to API and searchable parameter
Merge pull request #750 from Sancus/accountsapi

[Fix Bug 916806, Fix Bug 950229] Add external accounts to API and searchable parameter
[Bug 951445] Fix PEP8 styling issues
[Fix Bug 951445] Run flake8 on Jenkins
Merge pull request #752 from Sancus/flake8

[Bug 951445] Fix PEP8 issues and run flake8
[Fix Bug 950801] Implemented Tabzilla Translation Bar

Squashed commits:
[899580b] added canonical-url from bedrock
[60dfab6] [Fix Bug 950801] Implemented Tabzilla Translation Bar
[063f578] Cleaned up import lines to follow code style guide
[937cca7] added newlines at the ends of new files
[5688ab3] checked against flake8