add REST models from common module
add REST documentation for principals module
convert body parameters to form parameters
clarify return descriptions; remove body params
move picture info from content
move BasicUser from following module
follow up from review
convert TenantInfo to BasicTenant
review followup
make form params arrays
add required documentation
move permissions model to principals module
review followup
Merge branch 'master' of https://github.com/oaeproject/Hilary into restdoc-principals
review followup
Merge branch 'restdoc-principals' of https://github.com/sathomas/Hilary into restdoc-principals
Follow up on oae-principals REST documentation