feat: Set box to -1 for new positions

[cashpw]

I borked the graph for #82. This includes the same changes.

[cashpw]

Checking in -- is there anything you'd like to see changed in this pull request?

[l3kn]

I've been thinking about this for a bit.

Assuming it will take some time until we build an algorithm based on ebisu,
the next best (used my many people for a long time) algorithm seems to be the one used by Anki.

A notable difference in this algorithm is a separation of cards into multiple phases (learning, relearning, mature),
based (from what I can tell) on a box value (already part of org-fc) and a lapse count (incremented on each failed review).

To correctly implement this "-1" box feature, existing cards would need to be updated too,
based on information in the review history file.
Changing cards outside of a review is what I'd consider a breaking change and if we go ahead and do something like that,
we might as well go for the more powerful feature of a lapse count.

Determining if a card could be derived from this count because only new cards can have box = 0 and lapses = 0.

[cashpw]

the next best (used my many people for a long time) algorithm seems to be the one used by Anki.

A notable difference in this algorithm is a separation of cards into multiple phases (learning, relearning, mature),based (from what I can tell) on a box value (already part of org-fc) and a lapse count (incremented on each failed review).

Do you want this change to only change the PROPERTIES (e.g. add the lapse count) or would it also add a new algorithm to more closely match what Anki is using?