Small improvements to GExperts

Some of the experts in GExperts have seen small improvements lately:

The Goto expert now allows incremental search in the list by typing in the number field. This feature was contributed by Achim Kalwa.

The Grep search expert now takes the name of the currently selected control on the form designer if it is opened while the form designer is active. Again, this feature was contributed by Achim Kalwa. The idea was from Peter Panettone.

The Todo expert now has a filtering function. The idea was from Peter Panettone, who also provided an implementation. Unfortunately I had to reimplement it because his code did not work with older Delphi versions.

Thanks again to everybody who contributes to the project. I might take a while to commit such changes but I try to do my best.