Add move action checkboxes for character divs

This should add little checkboxes for the standard action and move action of a character.  To come: a function that clears all checkboxes (ends the round)... maybe add a thing up top that shows how many rounds have happened.
Changed div layouts

The added characters are now a div with two divs inside.  This messes
everything up! Yay!
Added rounds feature

Now the number of rounds is tracked as the game goes on, and actions can
be ticked off as they occur to keep track of when the round has ended.
Edited background

Now has a patterned background.  More styling to come later.
Styling, js revision

Discovered a bug where reordering by initiative increased the id of
every div, which resulted in deletion anomalies.  Fixed said bug.
Revised id assignment

Ids now assigned in a less confusing, less bug prone way.