Bug 948491 Join group

Implement joining groups that might require approval.
Add through model to group membership so we can track membership status.
Fix bug 948491
member vs requested classes and indicator are in place. gradients need to be made cross-platform.
Bugs 948491 and 938723 - curated groups, view and join
Add some tests
Fix user v. userprofile bug
Clean up after rebase
Fix a couple of bugs:

* template error when viewing search results
* set blank=True on group join date so it doesn't have to be
  set in the admin
Show pending users their own membership
Code changes in response to review comments

* fix group creation and add test
* add has_member tests
* reformat long lines and add setup.cfg to configure flake8 for max line length 100
* change var name in groups/0016 migration
Bug 938723 - Lots of good improvements in response to code reviews
fixed “requested” indicator when it’s a button
Bug 938723 - Remaining Python review comments

* Include curator in members
* Show all data in both groups and functional areas
fixed whitespace and translation formatting
added title to add_edit group
Added LESS prefixed submodule, fixed member request button on :hover