[UI] UI completely implemented

[JudiTeller]

closes #74

This PR adds a UI, that can be used in 3D space, as well as on Screen space.

In total this PR provides following features:

• a dismissible text box that can be triggered via the game code to display text to the player
• a game timer, that displays the current time provided by the game logic
• an integrity indicator in the form of a progress bar that can be updated by the game logic
• a navigation bar, that provides position information for active tasks