Allow for multiple metering points

[schulz-alexander]

Allow for multiple metering points,
PreAmp section should always show direct preamp level.

Channel fader should be configurable between PreAmp, PreDynamics(post HPF), PreFader or PostFader.

Native WING
"Open the Setup menu on the console.Navigate to the Surface tab.Locate the Metering option and toggle it between Pre-Fader or Post-Fader."

Originally posted by @DrEVILish in #85

[schulz-alexander]

• has to be implemented in OpenX32 (DSP1)
• after that we can implemnet it in OMC