Numerical tracker reducer

[RZarifov]

Currently we have a numerical tracker added not so far ago, but it tracks in increasing order, as I can see. There is no way you can track the numerical amount of something in reducing manner.
I mean for example you spend hours and hours watching youtube. And you want to bring this number from 4-6 hours a day, down to two hours a day. That would be neat feature indeed.

So in short what I mean is to set goal aiming on reducing numerical (or temporal) amount of something to spend less time on something with each passing day.

[KristianTashkov]

This is a duplicate of #949.
Implementation is in review here so it could be available in the application soon: #1101