Link fix

This PR is another step towards combined  effects. 
It replaces the invert linked hint and introduces a neutral hint instead. This set a point on the knob parameter that are adopted at neural point on the super knob. 
The super knob can be driven in two modes, a neutral center mode, usually used for EQs and Filter effect, or a neutral left mode used for effects like bit-crusher. 
If you like to combine a bit-crusher with an EQ, you can set the link type of the bit-crusher knobs to new left, right or left/right mode where the neutral point (1.0) of the bit-crusher is mapped to 0.5 at the super knob.  
All this can tested with the Shade skin. 

Yes this might be a cause of later errors. It would make the interface cleaner, but the code more complex. 
Remember that we have to use the behavior classes for conversion.
An other drawback is that we can't pick a sensible default unless we deal with the default state separate.
For now I prefer to fix it by tweaking the name. 
What about neutralParameterHint() 
or  superKnobNeutral()

By the way: What about renaming the super knob to super knob in the code base? 
we ares still alpha ;-)