Add ParseHeaders mode to copy multiple annotations into one

[Jason Vander Heiden]

Currently, you can copy multiple annotations into a single collapsed annotation via something like:

> ParseHeader.py copy -s file.fastq -f PRIMER BARCODE -k PRCODE PRCODE --act cat cat

This is non-intuitive and would probably be better as a separate command (merge maybe?)

[Jason Vander Heiden]

Done in 6fb72ab as ParseHeaders-merge.