[keycloak-dev] First round of unifying application and oauth clients

[Stian Thorgersen]

First round of unifying application and oauth clients is done. What I've done is:

* Combined ApplicationModel and OAuthClientModel into ClientModel
* Removed OAuth Clients (html and js) from Admin Console and Admin Endpoints
* Renamed Applications menu entry to Clients in Admin Console

Next steps are:

* Add database migration
* Update Representations (deprecate OAuthClientRepresentation and ApplicationRepresentation and add ClientRepresentation)
* Rename Application to Client in Admin Endpoints and Admin Console html/js
* Look for other references to Application or OAuth Client in code
* Update documentation, including migration guide