Adds the option to render the mixer levels in dB FS. By default this
option is disabled so that classes which inherit from Fader are not
affected by this change. However, in the code of the FxMixerView this
feature is enabled so that the mixer shows the levels in dB FS.
The ability to render in dB FS is exported as a property so that it can
also be set in a style sheet (not used as of now). The new property is
There are now setters and getters for the min and max level.
Showing the levels in dB FS (which is a logarithmic scale) gives a less
"fidgety" impression when the levels are moving.