Merge branch 'open-data-api-all' into 'master'

API support, serving JSON formatted data

Paged api endpoints accept "page" and "pagesize" params.
New config file config/settings/open_data.global.php
ACL is dynamically manipulated by the module.
The "index" endpoint provides links to available endpoints.
Documentation is provided in swagger.
Add doc links to open data page itminedu/gredu_labs#14

See merge request !18