fixes #78, but maybe we rethink this together:

[pSpitzner]

our progress levels / stages are not super intuitive.
we already modify the library at the end of "waiting for user selection" - at which point apply_choice is invoked (does not move files, but adds to library)

we should consider to split the user_query stage into more parts.
currently it contains:

• choose_match logic
• duplicate resolution
• potentially merge duplicates (not tested)
• apply_choice (which modified beets lib, without moving files)

my fix was to check the threshold before the user_query stage alltogether, but im puzzled this works, as candidate selection (on which thresholding should depend) only happens during choose_match.

[semohr]

Kinda makes sense that it should happen before or during user selection. Maybe it would make more sense to overwrite the choose_match function in the AutoImportSession instead of having a stage for it altogether?

• offer matches: gets all candidate (best one is the first one)
• match threshold: checks distance of best candidate against the config threshold
• user query: too much logic including choose_match