Allow width of Parameter Slicer to be set to the size of the one input box it hosts

[jeff_weir1]

The minimum allowable width for the #PowerBI Parameter slicer seems to use the same setting as the *old* Slicer, even though it only has one input pane and plenty of space to spare.

We need to be able to make this slicer just a little bit wider than the one input box it hosts.