bug-fix, bug-fix, animation

The new feature of this release is that color-changes of objects and the opening/closing of frames is animated. From a developers viewpoint it is annoying how sensible the human brain reacts to instantaneous changes, so I guess this feature had to be added at some point. 

The visual appearance of the animation needs more tweaking and the animations can, at the moment, not be interrupted, which slows down the gameplay. But these things will come in a later update.

I slightly changed the design of the frames. The frame design is less symmetric now, so that it is visually evident where the bottom of the frame is, even if you stand inside of it.

Otherwise, this update contains several bug-fixes that piled up over time:

• there was a weird camera rotation if gravity was rotated by exactly 180 degree
• the box containing the text of the hint machine was too small in several cases
• when "sliding" above a frame it could happen that the character slides up slopes afterwards
• some unwanted collisions. These collisions could only happen in the Editor, but for a better workflow they had to be fixed.
• sometimes the speed of objects below the character weren't calculated correctly, resulting in the character sliding on those surfaces
• The cross-hair was positioned inconsistently, resulting in a jiggly movement of the cross-hair
• the position of the force-fields (the indicators if an object cannot pass a frame) weren't updated in parallel to the camera movement, resulting in a jittery movement
• head of character wasn't oriented along the camera direction if the character was standing inside a frame

All these bugs are no more.