API endpoint for listing all the groups that user belongs to (BB-11328)

It would be useful to have endpoint that will list every group that user has created or is a member of.

Also you might want to update documentation regarding this endpoint:

• endpoint: GET https://bitbucket.org/api/1.0/groups/ {accountname}
• doc page: https://confluence.atlassian.com/display/BITBUCKET/groups+Endpoint#groupsEndpoint-GETalistofgroups

Part "The caller must authenticate with administrative rights on the account or as a group member to view a group", seems misleading since it made me believe I would get all the groups I am a member of.

Have a good day!