Add an "edit" mode to the curses front-end

[calebsmith]

Essentially, this should allow a user to edit and save the seed data file that is loaded. A session would look something like:

gameoflife data/filename.dat

Make edits, save and quit. filename.dat is now updated with the edits made.

This will likely need to have the cursor enabled in curses, and move the cursor with hjkl and arrow keys

[calebsmith]

On second thought, the "edit" mode might work with the graphical mode as well, via the mouse. This should be kept simple though. Golly satisfies the requirement of seed file editing much better already