Massive change in files: all GUI stuff is now in the UI class.
Also moved utlities out of fluids.js into its own file.
UI object now provides source for density when clicked.
Fixed UI interaction with sim and grid to add density sources.
Added debug value display to grid rendering.
More debugging of diffuse to no avail.
Re-enabled adding velocity (per click) in UI.
Buggy as well. Sigh.
Tweaked "a" in diffuse, works a bit better now.
Updated GUI and simulation parameters.
Fixed rendering for the grid.
Cleaned up Project code. It's hopeless...
Removed fixed density source from UI/params.