rename community_footer.html snippet to footer.html
check if SystersUser is member of a community + unittest
fix flake8 errors
get SystersUser last join request to a community + unittest
Community join button html snippet
add "change_community_page" to content manager permissions
fix documentation about groups and permissions
Community actions sidebar HTML snippet
fix HTML validation errors
add unicode representation to CommunityPage model
show community landing page and specific community page

Includes:
* routing
* template
* view
* unittests
Merge branch 'community-pages' into develop