Make all parameter search/filtering async

[wucke13]

It's very annoying if one has to wait for the search to yield results. Especially if the whole UI thread is blocked. That's a no-go.

[Arne-W]

@wucke13 Which search do you mean? If you mean the loading bar on the left bottom - this is not a search bar it shows the progress of parameter downloading from the UAS.
We have to wait until all parameters are downloaded otherwise we can not populate several views.

[wucke13]

Obviously I do not mean the bar at the bottom, but the text box with the default string "Filter" in the upper right area of the Standard Params & Advanced Params panel.

This one: