[API] - minor fixes

- fixed api index action still refering to old restsapi gem
- currently forced apipie to load DSL so we can reuse its DSL in our views

api v1 - render errors with rabl

better detection of permission failure in model
fix ApiConstraints
catch bad routes in api and return json

api v1 - render home#index links from restapi

fixes #1775 - API versioning name space