WU: AULowShelfFilter 4+

WU Series Maintenance Update 1.2 (January 2021)

- fixed a multiple instances problem with the editors
- fixed a wrong icon assignment of the highpass filter unit
- fixed a parameter assignment bug, if the units define special addresses
- fixed possible adjustment of read-only parameters
please note, that read-only parameters are still displayed with the interface
- added parameter min/max value validity checking
- re-adjusted finer control of the sliders
- added support for string values
- added support for labels for indxed parameters
- re-adjusted some label sizes and positions
- added fixed point formatting for floating point parameter values
- completely removed resizing control from the UI
- disabled gestures for resizing and positioning internal view
- reduced diagnostic printout during load
- removed MIDI assignment extension due to problems with some hosts,
which send unwanted MIDI controllers and initializers to chained effects
- all WU units are now exposed a standard audio effects (aufx),
effectively increasing the amount of hotsts supporting them
- please note, that any extensions to these units would
make the aupreset format incompatible with the original
and no longer share-able across platforms and hosts

- added the AUPitch shifter unit to the collection
please note that the pitch shifter has one parameter,
that is not intended for realtime use
- added the AUMIDISynthesizer to the collection
this unit is a multitimbre multi MIDI channel sound module
with a standard General MIDI compatible sound bank.
- added the AUSampler unit with a set of GM based presets
please note that this release is a preview release for the
capabilities of the sampler unit and its file format