Added a second EQ Effect per deck, alias to filter controlls
readded filter controll to the control picker menu
Added second ComboBox for Filter knob effects
Added Alias controlls to development tools
Load filter effect from dlgprefeq
Merge remote-tracking branch 'upstream/master' into flter_rack

Conflicts:
	src/effects/effectmanifest.h
	src/effects/native/bessel4lvmixeqeffect.cpp
	src/effects/native/bessel8lvmixeqeffect.cpp
	src/effects/native/bitcrushereffect.cpp
	src/effects/native/filtereffect.cpp
	src/engine/effects/engineeffectchain.cpp
Allow to select "None" as filter effect
Add ScannerTask, ScannerGlobal, ImportFilesTask and RecursiveScanDirectoryTask.
Parallelize the recursive scan step of the library scanner.

Uses 10 threads currently.
Add benchmark TODO.
Merge branch 'eq_rack2' into filter_effect

Conflicts:
	src/dlgprefeq.cpp
	src/dlgprefeq.h
	src/effects/effectmanifest.h
	src/effects/effectsmanager.cpp
	src/effects/effectsmanager.h
remove gcc warning in BaseTrackPlayer
Shade: some minor clean ups
Put different headings onto the combo boxes for EQ and filter
Merge branch 'eq_rack2' into filter_effect

Conflicts:
	src/dlgprefeq.cpp
	src/dlgprefeq.h
	src/effects/effectsmanager.cpp
	src/effects/effectsmanager.h
renamed filter function
remove getAvailableFilterEffectNames() in favour of getEffectNamesFiltered()
Deere skin: Add TooltipId to <Time> widget in the toolbar and move it to the outer right. Delete invalid <Battery> key.
Deere skin: Add stereo/mono split button to the headphone controls in the toolbar.
Deere skin: Don't display the cover art by default beneath the <Spinny> widget because we display it in the text row already. Add a comment if you still want to archive that.