Huge update. DWA, structural changes, etc.

Changed structure of project, moving basically everything from utils.py
to seperate modules.

Added possibility of running system integrator at a different rate than
vessel controllers (e.g. h=0.05 and dT=0.5).

Added possibility of discretizing map for faster testing. DWA tests
for collision about 13 000 times per iteration.

Implemented the Dynamic Window Approach (ctrl_DWA.py), but still needs
tuning. Is currently a bit slow (update() takes ~500ms).

Animated simulations is now possible!

Probably a lot of other new features as well.