Major Description
Currently the PropertyState contract specifies that an IllegalStateException gets thrown if a single-valued property is accessed as a multi-valued one (and vice versa).
This leads to cumbersome if statements in code that simply wants to go through all the values of a property. To avoid that complexity it would be useful if, instead of throwing an exception, the getValues() method simply returned an iterable containing the one value of a single-valued property. A client that wants to explicitly check that a property really is multi-valued can still do so simply enough by calling the {{isArray()} method.
A somewhat similar case can be made also for getValue() on a multi-valued property, but that's a bit trickier so let's leave it outside the scope of this issue.