Not plugged into the Python code yet. Still a work in progress.
Other changes:
- move a bunch of From implementations out of the giant backend/mod.rs
file into separate submodules.
- reorder backend methods to match proto order
- fix some clippy lints
Closes#766
- changes the on-disk representation from % to a multiplier,
eg 250 -> 2.5, as this is consistent with the other options
- resets deck configs at or below 1.3 to 2.5
- for any cards that were using a reset deck config, reset their
current factor if it's at or below 2.0x. The cutoff is arbitrary,
and just intended to make sure we catch cards the user has rated
Easy on multiple times. The existing due dates are left alone.
