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. 

All these values already have their default values defined in EffectManifestParameter()
```
            : m_controlHint(CONTROL_UNKNOWN),
              m_valueHint(VALUE_UNKNOWN),
              m_semanticHint(SEMANTIC_UNKNOWN),
              m_unitsHint(UNITS_UNKNOWN),
              m_linkHint(LINK_NONE),
              m_neutralHint(0.0) {
```
we may change them, but that is out of the scope of this PR