add sequence pretty printer
MANTA-58 improve debug msg
MANTA-58 additional debug info
MANTA-58 add a new split edge size check
MANTA-58 adjust off-by-one in contig bp offset
MANTA-58 demo a new split edge size check
MANTA-58 first pass at a fix

add 100 bases of flanking refernece seqeunce at the assembly stage
which is reserved for split read alignment and not available for
breakend discovery (ie. not part of the contig alignment)
MANTA-58 debug msg
MANTA-58 fix off-by-one in scanEnd, assert conditions