Fix #42, toggling collision checkboxes ignored.

Only one line of this change is important to fix the bug: the second connect() call connecting the previously-unused function toggleCheckBox().

The rest of the change lines are changing whitespace and changing parameter names "j" and "i" to "row" and "column" for clarity.

I tested this and it seems to work.  Changes are preserved when you go to a different tab and they are also written to the .srdf file.

The only thing to watch out for when testing is that "Show Non-Disabled Link Pairs" is off by default, so if you see the big list of disabled pairs and all the check-boxes are checked, then you un-check one of them, then go to another tab and come back, you will see that they all look to be checked again.  However, if "Show Non-Disabled Link Pairs" is off, the one you had un-checked is now hidden.  It's easier to see that it is working correctly if you enable "Show Non-Disabled Link Pairs".