Add option to have Tab skip over filled clues

[mrichards42]

Feature request from an email:

It would be really useful to have Tab skip over filled clues, or at least to have that as an option. That was always one thing I really didn't like about Across Lite, as compared with the NYT software or PuzzleMe.

[jpd236]

I think the PuzzleMe navigation is more than just the Tab button - it's about having the "Skip filled letters" option control every form of navigation (except arrow keys?). So Enter will skip over any entirely filled words; Shift+Tab will move backwards and skip over any filled words, etc.

There's also an option in terms of what to do at the end of a word - XWord keeps you in the same word, but PuzzleMe has the option of moving you to the next word (effectively hitting Tab/Enter).