Fixes bugs where during project loading (observed with VST effects), empty
widgets and sub-windows would be left floating around. These were caused by
inconsistencies between the way VST UIs were created when loading a project
and when adding an effect in an existing project. In some situations, this
caused createUI to be called twice, leaving over multiple empty widgets.
This commit refactors some code in order to avoid creating unnecessary sub-
windows, which aren't needed with VST effects, but were still created,
usually being invisible. All sub-window related code was moved out of
VstPlugin into vestige.cpp, which is the only place where sub-window VSTs
are actually used. A new sub-class of VstPlugin, VstInstrumentPlugin, now
handles VST sub-windows and is used by vestigeInstrument.
"guivisible" attribute loading was moved out of VstPlugin as well and is
now done in VstEffectControls' and vestigeInstrument's loadSettings method
respectively. This causes some minor code duplication unfortunately.
Closes#4110
Fixes 20 warnings similar to the following ones when generating a translation file with e.g. "make de.ts":
/home/daniel/Lmms/src/tracks/AutomationTrack.cpp:40: Class 'AutomationTrack' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/FxMixer.cpp:41: Class 'FxRoute' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/FxMixer.cpp:554: Class 'FxMixer' lacks Q_OBJECT macro
/home/daniel/Lmms/src/gui/widgets/MeterDialog.cpp:52: Class 'MeterDialog' lacks Q_OBJECT macro
...
Fixes 20 warnings similar to the following ones when generating a translation file with e.g. "make de.ts":
/home/daniel/Lmms/src/tracks/AutomationTrack.cpp:40: Class 'AutomationTrack' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/FxMixer.cpp:41: Class 'FxRoute' lacks Q_OBJECT macro
/home/daniel/Lmms/src/core/FxMixer.cpp:554: Class 'FxMixer' lacks Q_OBJECT macro
/home/daniel/Lmms/src/gui/widgets/MeterDialog.cpp:52: Class 'MeterDialog' lacks Q_OBJECT macro
...
