Use Hilt instead of Koin (#93)

* Use Hilt for DI
* Use Hilt for settings providers
* Use Hilt for login credentials fragment
* Use Hilt instead of ServiceLoader for intro fragments
* Rewrite from Koin to Hilt
* Tests
* Use more Hilt modules for service loading (account drawer, intro fragments)
* Lint
* WebDAV provider: don't listen to changes in onCreate (causes problems with Hilt and tests)