union: Documented that it's multi-safe (supports an input appearing multiple times)

mappings/DwC2-VegBIEN.specimens.csv: Moved shared /specimenreplicate root to mappings in preparation for reversing the XPaths so that parent table paths (such as location) don't contain a prefix for child tables (specimenreplicate, locationevent, etc.). This reversing will avoid the need to "ch_root" the child table map to obtain maps for parent tables with the prefixes removed, allowing all hierarchical levels to use the same map spreadsheet.

ch_root: Support column headers without a root, for non-hierarchical formats such as DwC

lib/common.Makefile: rsync: Time the rsync operation

in_place: Wrap EXIT handler in shell function so that "-escaping can easily be used on the temp file path

in_place: Documented that doesn't update file on error

DwC mappings: Removed ':/list/' root (full version: '::[@xmlns:dcterms=http://purl.org/dc/terms/]/list/') from map spreadsheets to simplify the boilerplate in each file. Since intermediate DwC XML files no longer need to be produced for automated tests, these roots are not needed.

inputs/import.stats.xls: Updated with stats from latest import

inputs/import.stats.xls: Moved independent-import data to separate tab so that it wouldn't get moved to the side whenever a new column of simultaneous-import data is inserted. It is also no longer updated, because all column-based imports are now done simultaneously.

Use strings.ustr() or strings.urepr() everywhere that columns are stringified, in order to support column names with non-ASCII characters (such as in the Madidi data)