On non-Linux platforms configuration file was saved in the application
path which definitely is not desired and also will not work in many
situations. Therefore always save ZynAddSubFX configuration file in
LMMS working directory.
It's now possible to hide the ZynAddSubFX UI by simply closing its main
window instead of going back to LMMS and toggle the "Show UI" button.
Furthermore moved code for GUI thread into a non-static member function
of RemoteZynAddSubFx and removed the old code for handling IdHideUI
messages.
Added a new GUI-less mode to ZynAddSubFX instrument plugin which allows
to let ZynAddSubFX audio processing happen within LMMS, giving a much
better realtime behaviour.
As soon as showing up the GUI settings of GUI-less ZynAddSubFX instance
are saved and a traditional RemoteZynAddSubFx process is being launched
and the settings are applied there.
