On capturing parametric remote warn on entering already known captured signal.

[bengtmartensson]

Probably there should be a confirmation warning the user that the signal has already been entered, allowing him to enter it again, if really desired. Also non-unique names should be detected.

This behavior should be the default, but possible to deselect it, reverting to the old behavior (= no indication of repeated signals).

[bengtmartensson]

Should be implemented in conjunction with #73.

[bengtmartensson]

Better to do this in the context of general overhaul of the remote editor.