Move the rendering of the envelope graph into it's own class.

This is a preparation step to use layouts in `EnvelopeAndLfoView`. It does not work with the mixed in painting in the paint event.

Move the LFO graph into its own class. This finally enables the removal of the mouse event and paint event code in `EnvelopeAndLfoView`.

Make the enum `LfoShape` in `EnvelopeAndLfoParameters` public so that it can be used without friend declarations. Add accessor methods for the model of the LFO.

Use layouts to align the elements of the `EnvelopeAndLfoView`. This removes lots of hard-coded values.

Add helper lambdas for the repeated creation of `Knob` and `PixmapButton` instances.

The spacing between the envelope and LFO should be removed once there is a more open layout.

Use layouts to align the elements of the `InstrumentSoundShapingView`.

Draw the info text at around 20% of the LFO graph's height. This prepares the dialog to be scaled later.

Write "1000 ms/LFO" instead of "ms/LFO: 1000" with a larger gap.

…apingWithLayout

Conflicts:
* src/gui/instrument/EnvelopeAndLfoView.cpp
* src/gui/instrument/InstrumentSoundShapingView.cpp

Whitespace and formatting.

* Remove some "pragma once" for now
* Adjust include orders
* Variable initialization in headers
* Prevention of most vexing parses