Implemented edit modes of Y generator and gates for Marbles via context menu

[eggix]

Implements the ability to edit Y generator and Gates as described in the Marbles manual. Instead of holding the bottoms on the physical interface, the edit modes are accessible via the context menu. In addition it fixes #91.

• Divider ratio for Y generator can be either adjusted via Rate knob in Y generator edit mode or via the context menu as before. Both methods are synced with each other.
• The two edit modes could also be combined into a single mode, since non of the used knobs in both modes overlap.
• The color of the knobs in the edit modes change for clarity. The colors are chosen arbitrarily, since there is no reference.
• Y generator is initialized according to

smooth, full-range (-5V to +5V), random source that is clocked at 1⁄16 the rate of X2

[eggix]

Thanks for your remark. uint is apparently not typedef'd to unsigned int by all compilers.