Removes '(forces -S)' from samtools view -T|t usage
Updates documentation for `samtools view`

Adds all missing options to samtools man page under the
`samtools view` section.

Adds all missing options to `samtools view` usage and updates
notes to better reflect reality.

Closes #155. Although we should definitely split the samtools
man page into sub-pages for each command.
Improves performance of `samtools merge` (slightly)

Moves call to pretty_header so that it is done once at the end rather than
once for each input file. As a result, 'trans_tbl_init' no longer returns
prettified headers. This results in a performance improvement when merging
many files, although performance still becomes very poor when merging on
the order of hundreds of files.
Tweak `samtools view` documentation formatting

Use italics instead of <brackets>, don't also quote emboldened options,
remove trailing whitespace.
Merge view documentation updates (PR #218)