Updates in api for roles and permissions

 - usergroups#show lists associated roles
 - listing available resource types
 - filters#show lists associated roles
 - filters#index lists associated roles and permissions and orders the results
 - pagination in permissions#index
 - missing parameters in apidocs for usergroups and roles
 - required name for usergroups
assert !xxxx.empty? => assert_not_empty or refute_empty  , ditto for the other tests.

Could you refactor the last lines of each method? All of them do essentially the same, checking response is ```:success``` checking ```assigns(:xxxxx)```, parsing the response, and checking the response is not empty.