fix: inputs/import.stats.xls: removed spurious diff comment on total time, which only applied to the previous import

inputs/import.stats.xls: reformatted times longer than one day as a # of days instead of hours, for clarity. the days format is chosen automatically when the # hours exceeds one day.

bugfix: inputs/*/Source/: added missing ./run, which creates the new-style staging tables with the metadata fields as part of the table. this is needed now that these subdirs use installed staging tables instead of metadata-only map.csvs.

bin/map: removed no longer used support for map.csv input column prefixes (expand out the prefixes instead). this used to be used by SpeciesLink to use just one mapping for a single term with multiple DwC namespaces, but was replaced with an explicit, ordered rather than implicit, unordered /_alt-ing together of the terms.

bin/map: removed no longer accurate comment that this is case- and punctuation-insensitive, since the case- and punctuation-insensitivity is now instead handled by map.csv preprocessing scripts before the mappings are even provided to bin/map

inputs/.herbaria/: switched to new-style import, which renamed the columns to the VegCore names. this is done using the commands at wiki.vegpath.org/2013-06-27_conference_call#To-do-for-Aaron > "run the following for each datasource".

lib/sql_io.py: cleanup_table(): don't run the slow ALTER TABLE statement again if the table has already been cleaned up. documented that it is idempotent (and actually was before this change as well).

lib/sql_io.py: added table_nulls_mapped__set(), "__get() wrappers around the corresponding util schema functions

lib/sql_gen.py: added table2regclass_text()

schemas/util.sql: added table_nulls_mapped__get(), which gets whether a table's NULL-equivalent strings have been replaced with NULL