add REST documentation for tenants module
remove server from REST endpoint keys
move Tenant model to common models
convert form parameters to body parameters
change string|array to array
move REST models to separate file
add REST models from common module
convert body parameters to form parameters
follow up from review
Merge branch 'restdoc-tenants' of https://github.com/sathomas/Hilary into restdoc-tenants
Follow up on Tenant REST API documentation