Standardize SFU MOD tags in core modifications

Wrap modifications with comments that start with "SFU MOD CANVAS-XYZ"
and end with "END SFU MOD". Use "SFU MOD - CANVAS-XYZ" for one-liners.
Override is_api? to force api calls to use authentication

Uses the same trick as sfu_api to force is_api? to return true.
Merge pull request #118 from va7map/standardize-sfu_mod

Standardize SFU MOD tags in core modifications
Merge pull request #119 from grahamb/stats-api-auth

Override sfu_stats api_request? to force api calls to use authentication
Revert "Removed Group API"

This reverts commit 7c6272100de9e2336625abffc9849e4d8eb20bff.
Added group_membership_id to Groups API

Also added condition to retrieve only 'available' groups and 'accepted' group_memberships
Changed workflow_state condition to != deleted

There could be other states other than 'accepted'
Simplify Group API: query GroupMembership directly
Merge pull request #1 from va7map/group-api

Simplify Group API: query GroupMembership directly
Merge pull request #120 from ronvs/group-api

Added group_membership_id to Groups API