[feature] Inverse Tracks

[andunix]

Some tracks (like "drink alcohol" or "drink coffee") are negative, which means that not ticking is good. I would like to see an option to mark those tracks as negative oder inverse. The UI then should switch the colors of the ticks: not ticked is cyan and ticked gets dark.

This leaves one question open: How do we deal with multiticks? Should they get dark with the first click? Probably a "goal" like in issue #24 would be helpful. Then the positive ticks get cyan after reaching the goal and the negative get dark when reaching the limit (inverse goal).

[DataStrategist]

This is an old issue, but let's seperate this out a bit into two issues. One is about variable color depending on state... harder to implement...

but the other is simpler... now that we have the ability to go up and go back down through inverse clicks... could we go down below zero just by changing that counter type? This is mentioned in #47