Add ability to create a mix for one or more pitch curve points on Wave

[Mardy]

When doing precision or scale flying it is nice to have the ability to tune the pitch curve around the hover point. So rather than having a mix that applies to the whole pitch curve it would be nice to be able to adjust a croup of pitch points. It might even suffice to be able to adjust just one point in the curve.

[ZeXx86]

Thank you, we will add the feature.