Continued work on Player tab

Also started work on Player class. I'm considering making it
serialisable in order to save/load efficiently. For some reason I like
the idea of storing data in binary, human-unreadable format.
Continued work on Player tab

By default all controls will be disabled, and the user will have to
either select "New ..." or "Open ..." from the file menu to unlock them.
"New ..." with the DM tab open will prompt the user to clear all lists
and reset the round number to 1.

I'm debating whether to add a "Dayables Tracker", a progress bar that
tracks abilities with limited uses per day. If I do that, I want the
user to have the option to add more in case they have more than one
dayable and/or magic item uses they want to track too.