Separated manual QC metadata from warehouse metadata because updates
are too slow, even when the data are ordered to get the most out of
the caching.

Added a new script to find recently updated plates only to handle
this.

Changed iRODS object search by metadata to return its path list sorted
by data object name, rather than using the order returned by imeta.
Updated the SNP database query to limit results to the latest plate
status.
Merge pull request #248 from keithj/devel

Separated updates of manual QC metadata from warehouse metadata