FLUIDSYNTH: Add separate dialog for FluidSynth settings

I don't really understand what these parameters do, or what the
sensible values are, so for now the sliders are limited only by
the allowed (or, in one case, "safe") values.
BADA: Add completely untested layout changes to Bada theme

I've simply copied this from classic_layout.stx. It probably needs
a bit of tweaking.
GUI: Make the FluidSynth settings dialog a bit more like Qsynth

To help people familiar with Qsynth (I'm not, but it seems to be
one of the more polished FluidSynth front ends), use the same
presentation and terminology for the FluidSynth settings.

More to follow.
GUI: Swap Reverb and Chorus tabs in FluidSynth settings

Again, this is to be more like Qsynth.
GUI: Add "Reset" button to FluidSynth settings dialog

This resets the FluidSynth settings to their default values.
GUI: Misc FluidSynth-related cleanups.
GUI: Move the FluidSynth reset button from Misc tab to bottom

This should make it clearer that Reset applies to all of the
FluidSynth settings, not just the Misc tab.
Merge branch 'eriktorbjorn-fluidsynth-settings'

This is a manual merge of a slightly adapted pull request #296.
The changes made are:
- Each time the theme format changes, the version was increased
- default.inc has been regenerated in the same commit as the theme changes