Fix incorrect specification of property types

[#48361799]
signal-generator: fix unitsDefinition

[#48361799]
time, displayTime, signalValue s/b outputs

[#48361799]
whitespace/indentation
Validator: new 'propertyChangeInvalidates' flag

Use this to distinguish properties whose changes require recomputation of simulation state from those whose changes don't.
signal-generator: use metadata for properties

[#48361799]
signal-generator: ensure signal continuity

[#48361799]
signal-generator interactive: add slider, output

[#48361799]