* Added saving of changed newznab categories in backend.
Added gui for selecting categories from multiselect box.
Created some helper function in js, for dynamically modifying selects/options

Made results of function for retrieving newznab capabilities more generic. In that now always a valid json is returned with success,tv_categories,error

Added gui elements for retrieving and displaying newznab capabilities

Added backend functions for calling ajax /getNewznabCategories?name=yourNewznabProvider&url=https://newznabprovURL&key=YourApiKey
Returns json.dumps() with TV category capabilities of newznab provider. Is going to be used for new gui element in adding newsnab provider.