replace hard UTF-8 literal with Unicode literal

no reason we should be making code encoding-dependent.
On second thought, move possession out entirely

It didn't belong in the function where it had been written in. RPI shouldn't
suddenly become dotRPI everywhere just because they have possession. It's up
to the template to decide how to indicate possession. </rant>
Add possession method to TeamHelper

this allows the template to decide how to do its own possession dot
Factor teams out into a class

This eliminates a lot of repeated code and lets us reset the game state.
This should have been committed many revisions ago...

specifically as part of 58f1495
ask if game data should be reset when changing sports

Since the UI for certain pieces of game data disappears when switching sports,
it's usually a good idea to reset that data to sane defaults before switching.
This avoids the possibility of extraneous graphics that are difficult to
remove. Fixes #23.
scoreboard_server: use bytesize instead of length

This was causing crashes when \uXXXX sequences were used
allow arbitrary instance variables in a team

This allows arbitrary instance variables to be pushed to a team via json.
This replicates the old behavior more closely.