These classes are unique to the context and adding the verbosity of
"Game" does not clarify anything so the prefix can be removed.

keyPressed fires before the text field is updated whereas keyReleased
fires after it. The previous approach meant that using a
single-character username was not possible because the validation saw an
empty field. Now it is possible.

All the code to run the timer was in place, it just needed an extra
if-statement to avoid trying to shoot when the timer ran out on another
player's turn.

This makes automating set-up for testing a bit easier as it skips the
need to input a username.

To test for username vailidity, I reused the logic from
TrackTestLoginPanel and moved the validation logic into a separate
class.

This also removes the System.exit calls from Launcher.call; those code
paths were impossible to test since the whole Java instance was getting
terminated. By returning an integer instead, we can check the return
codes in tests.

When this was fully commented, Maven was recompiling the entire source
every time it was run because the file was invalid.
See https://stackoverflow.com/questions/17944108/maven-compiler-plugin-always-detecting-a-set-of-sources-as-stale

Since the class is unused, it can be deleted. This speeds up the
iteration cycle of server development by a few seconds.

The fixes championship games in single player.

This is in preparation of making the "Try Again Now" button on the
canvas work.