Fix fade-out for some menu elements.
Add an entry for the custom level to the level select screen.

The entry is on the last page, and it is always unlocked.
Mainly change the display of the messages in the corner.

They are now drawn with a transparent white background, making
the words easier to read when they overlap with the launcher.

Also, the "Collision!" text was moved to the lower-left corner, and
it was also reworded. Some strings were also rephrased as well.
Fix a logical error with FindNextLevel().

Instead of returning null when the level name isn't in the LevelGroup,
it returned the first level instead, causing the Next Level button
to appear after the custom level was completed, which doesn't really
make sense.
Add some files to the Setup project.