Add metadata to extracted overhang reads

[Adamtaranto]

teloclip-extract will write reads with terminal clipped-overhangs to fasta files. To aide in sanity checks we should include some metadata to the fasta header.

Proposed fields:

• Anchor len: how much of the read is aligned to the ref sequence
• Overhang len: how long is the overhang
• Ref name: which sequence is it aligned to
• Motifs : Motifs of regex patterns used in filtering (comma delim list)
• Motif counts: Total count of motif matches in overhang (list matching order of motifs)

Other behaviour changes:

• Sort fasta by overhang length
• Include reference segment in output fasta (from earliest alignment start coord)
• Log total read counts for each end of each reference sequence.
• Print histogram of overhang depths
• Log warning if unbalanced overhangs (i.e. most ends have 5 and one has 500 reads)

[Adamtaranto]

Include option to only output longest overhang per contig end.