Development login, register, welcome and splash screen

[MartinKoleff]

In this branch l have:

• created logo and app icon
• splash screen with custom animation and view model wired with caching for credentials and tokens
• login screen
• register screen
• custom auth validation
• testing for all auth use cases and auth validation
• user and token room DBs.
• welcome screen with video played in the background (custom video edited on fiverr)
• wired navigation based on cached credentials
• error and success dialogs + wired with screens