Added player portraits and names

-New portrait assets are created (for now, based on sketches provided by
our character artist), then placed on the main bar.

-Player names are placed in the empty space below the main bar, next to
their respective character portrait.

TO DO:
- Implement a bullet counter.
- Move core timer stuff over to the freeze code/get ready script
- If possible, implement "READY.... GO!" text for freeze code at the
start of the game
- Move stellar stuff from placeholders if Chico's code is ready