Refactor Grid inline editing

Do not clear the rows that failed validations.
Cleaner use of endpoints for data processing.
Refactor Grid operations

* internal changes
  * Endpoints renamed in Grid:
    * `post_data` => `server_create` and `server_update`
    * `get_data` => `server_read`
    * `delete_data` => `server_delete`
* SECURITY FIX
  * when a grid had a scope set, it was possible to delete/edit a record outside of the scope by tweaking its id during
  request
* improvements
  * Do not loose rows in grid when attempting to create records that fail validations
Use netzke-core master in Gemfile