sql.py: Parse "function already exists" errors as DuplicateFunctionException

sql.py: mk_select(): joins: Fixed bug where join_not_equal did not do what it was designed for, which is filtering out matches of the join condition (before the bug fix, it effectively did a cross join with matching rows excluded, causing duplication of rows). Renamed join_not_equal to filter_out to reflect its intended use. Support table-scoped column names in the WHERE conds list.

sql.py: put_table(): Fixed bug where ORDER BY column needed to have table0 name prefixed (if it didn't already have a table name), to avoid ambiguous column references

sql.py: mk_select(): Fixed bug in joins where right_col had the table name prepended before it was copied for use with a different table name in join_using and join_not_equal

Mapped some unmapped fields in DwC inputs

Added mappings/for_review/DwC2-VegBIEN.specimens.fields.csv

db_xml.py: put_table(): Fixed bug where didn't commit right after inserting node, but instead waited until children with fkeys to parent (independent of the node itself) were inserted

sql.py: put_table(): insert_(): Use insert_select() instead of run_query_into() if new option pkeys_table_exists is on

sql.py: mk_select(): Support joins with !=

sql.py: mk_select(): Support only some join columns being join_using