DDR mode bugfixes & baby difficulty

[Ruzihm]

Adds very easy difficulty, makes press feedback consistent, fixes misplaced pulse indication.

Also renames difficulties to be doom themed

[AEFeinstein]

Love the difficulty names!

This is throwing a warning because there's a fourth score saved now:

settings_t settings =
{
    .SaveLoadKey = 0,
    .isMuted = 0,
    .menuPos = 0,
    .savedDemon = {0},
    .ddrHighScores = {{{0}}, {{0}}, {{0}}},
    .gitHash = {0},
    .selfTestPassed = false,
};

Please also increment SAVE_LOAD_KEY, since the gitHash and selfTestPassed bytes are now shifted.

Other than that, looks great!