Overlapper adapter mods

[msettles]

Actually no changes to adapter, changes reflective of conversation had around stats reporting

• Updated overlapper stats, removed a few stats, put short, medium, long in its own block, changed some names.
• insert/overlapped stats are now relative to input and not output
• removed Cutting options from overlapper, so no min-length, stranded, no-orphans gone
• prevented a 0 length read, now if read result 0 length, outputs a N with qual 2 (related to no discard)
• fix a small issue in counter when append-stats-file is used, stats-file is written out too in parameter block, change to prevent it from doing so
• added option force-pairs to overlapper, to split a read down the middle (odd length R1, gets extra base). and changed to make sure output is the same.