4.5.2 - Filter low coverage diffs earlier

Moves the filtering out of diff files from Tree Nine into myco in order to prepare for an eventual split of myco and Tree Nine for CDPH. Also generates a (currently unused) error code output from this filtering step to be used by the in-development "put the sample filtering error in the data table" system.

PR

• Filter bad diffs before tree nine by @aofarrel in #34

Full Changelog: 4.5.1...4.5.2