Add ENV_package to sample sheet

@tanaes wrote
We're planning on modifying the downstream sample demultiplexing pipeline to automatically filter out human reads from human-derived shotgun sequencing. This should be able to be done on a per-sample basis automatically if we include this as a flag in the sample sheet.

To allow this behavior, we'll need to:

Modify sample sheet generation routine to pull metadata to look for host taxon ID
Add column to sample sheet with a 'filter human' boolean value
Modify the sequencing page to have a check box to disable automatic filtering (maybe?)

The hot_taxon_id is a required Qiita metadata field, and adding it to the sample sheet will enable per-sample human read filtering.