Added basic GameUserInterface class that displays the top panel
Display level name and lives in the top bar

- added generic query functions to the Themes class
- moved the game status to a GameStatus structure that is shared between the game and the ui
- updated the default theme
Assing current theme earlier to invalidate the old saved state
Merge branch 'feature/basic-ui' into develop
Better error output on json errors
Remove dead enemies faster
- projectiles now only hold a weak_ptr to their target
Cleanup the Enemy class removing the projectile count
Merge branch 'feature/weak-projectiles' into develop