inputs/VegBank/taxonobservation_/map.csv: Updated with new renamings of colliding join columns

join: When a join mapping exists but is empty, still include any additional columns from that mapping in the combined row

inputs/SpeciesLink/Specimen/src.csv, inputs/XAL/Specimen/src.csv: Use input term as the initial Veg+ term, so the src.csv can be used with the Add back automapped mappings process at <https://projects.nceas.ucsb.edu/nceas/projects/bien/wiki/Map_refactoring#Add-back-automapped-mappings-to-mapcsv>

inputs/XAL/Specimen/src.csv, map.csv: Switched from using root prefixes to full column names, because the namespace mapping functionality can be handled much better by treating each namespace-qualified term as its own term rather than as a term and a prefix

inputs/SpeciesLink/Specimen/src.csv, map.csv: Switched from using root prefixes to full column names, because the namespace mapping functionality can be handled much better by treating each namespace-qualified term as its own term rather than as a term and a prefix

inputs/SpeciesLink/Specimen/map.csv: Removed no longer needed duplicate entries for each first letter case, which cause duplicate output mappings now that join is case- and punctuation-insensitive. Note that the `svn diff` hides _alt entry 0, which contains one of the removed duplicate columns that appears in the diff.

inputs/SpeciesLink/Specimen/src.csv, inputs/XAL/Specimen/src.csv: Added Comments column for consistency with autogenerated src.csv format

join: Added new passthru mode which passes through terms with no input mapping or no join mapping

inputs/: Added [Veg+] to via map roots to indicate that the datasource and Veg+ vocabularies are combinable. This is possible now that automapped entries are no longer subtracted when this is in the map root, so there is no concern of losing comments on subtracted automapped rows. Note that this change turns on old-style automapping for these datasources, causing SALVIAS plotMetadata to acquire additional mappings.

canon, translate, filter_out_ci: Support vocabularies/dictionaries with additional columns in addition to the functional column(s) used by the program. These columns can contain comments, etc. This was not originally supported because Python 2's iterable unpacking only supports "an iterable with the same number of items as there are targets in the target list" (http://docs.python.org/reference/simple_stmts.html#assignment-statements). We now use numeric array indexes instead to get around this limitation, and for consistency with other map-manipulation scripts.