Progress bar for level loading

[smerkli]

When loading a level, Orxonox currently does not display a progress bar. Since it can take a while for a level to load, it would be nice for the user to see whether anything is happening.

A progress bar (as seen in other games) would improve the user experience. One would have to implement a progress monitor in code and also add the graphical component for it to the game, making this a possible two-person ticket. The loading screen could consist of two elements:

• A bar that shows the actual progress
• some flashing/rotating/otherwise moving icon to show the game is doing something even if the progress bar is standing still