#77 Entering protosegments

[Maria Faehndrich]

When I move into a protosegment field in the Tabulate
pane, I can not select an already established
protosegment by typing the letter. I have to move into
that field using the mouse in order to be able to do that.

If I remember correctly, this was not a problem in
previous versions (before 1.1.0).

Being able to use only the keyboard would greatly speed
things up in some cases. If I have to use the mouse for
the assignment of every single protosegment, even ones
that are already established, it does slow things down a
bit.