ENH: add --negate_sample_id_fp to filter_samples_from_otu_table.py

@ebolyen and I pair-programmed this.

Fixes #1117.
DOC: update script usage examples

Based on @gregcaporaso's suggestions.
Merge pull request #1805 from jairideout/issue-1117

ENH: add --negate_sample_id_fp to filter_samples_from_otu_table.py