Added context information to every Serial.print call where it was missing. Previously sometimes plain numbers were logged without any hint what they could mean.

Introduced enums to be used instead of magic ints to increase the comprehensibility of the code

Replaced if statements with switch, removed redundancies

Added a new modifier that TonUINO stops playing after the current track

The test was done after the call to the active modifier, so this was called twice. This can lead to unexpected behaviour of the modifiers. In fact the check can be moved to the Mp3Notify class. That way we also don't have to create random track numbers if the next button is pressed.

Added preprocessor directives that allow to simply activate a power led

If buttons four and five are pressed long while nothing is played, the system behaves as if the non-modifier card that was used the last time was used again. So it's possible to continue a card after the system went into sleep without having to use the card.

Set five button mode, changed button five pin, removed mp3.sleep