* Added support for Gotify notifications
* Removed non-supported features and adjusted priorities
* Use string interpolation to build url
* Rename a few variables and improve Url validation
* Improve building of the Url, move validation to Gotify.cs (adapting changes by markus101 over at Sonarr)
* Move validation from GotifyProxy.cs to here (adapting changes by markus101 over at Sonarr)