Initial version of Peaks.

[cschol]

Port of Mutable Instruments Peaks a.k.a. "Percussive Synthesizer".

A few comments:

• The code tries to reuse as much functionality as possible from the original source and does not require any modifications of the eurorack submodule to build.
• However, most of the content of the ui.cpp file has been ported into the Peaks.cpp. It was easier than trying to recreate all that complex logic from scratch.
• The output scaling might be a little off. I unfortunately don't have an actual device to compare it, but maybe can look for someone to help test.
• I created the panel design from the Peaks.ai file in the repository (modified with Photoshop). I don't know how the other panel PNGs were created. Maybe this one can be re-created the same way. The locations of UI components should be accurate though according to the panel layout. It is missing the module name on the panel as I didn't know what font the other modules use.
• The only thing that was not possible to implement was the access to the "Number station" secret mode by pressing the two small buttons at the same time for three times. I implemented this by a context menu option. Same with the snap mode, which requires holding a button on power up.

[cschol]

@AndrewBelt I'll update this PR to the v0.6 API in the next couple of days.

[AndrewBelt]

Don't worry about the panel, I'll do that.

[cschol]

Mmm...that PR didn't update as expected. I should have made the initial PR from a branch instead of master. I can redo the PR from the peaks branch if you want. That one includes all the latest v0.6 API updates.

[cschol]

45 is clean PR from peaks branch against master. Closing this one.