xml_func.py: Removed no longer used _map(), which has been replaced by a corresponding DB function

schemas/functions.sql: Added _map(), which uses the new hstore functionality. This expands _map() functionality to column-based import.

root Makefile: VegBIEN DB: DB and bien user: mk_db: hstore extension: Fixed bug where need to use `CREATE EXTENSION hstore SCHEMA pg_catalog` instead of createlang, because hstore must be explicitly created in pg_catalog or else it will be created in the public schema instead, causing it to get deleted every time the public schema is reinstalled and cascading the delete to everything (including in other schemas) that uses hstore

sql_io.py: put_table(): Added special handling for functions with hstore params. Note that although _map() doesn't exist yet as a DB function, this code must be in place before _map() is created to avoid param type mismatch errors.

root Makefile: PostgreSQL: postgres-Linux: Changed plpython to plpython3 in order to install plpython3u

schemas/py_functions.sql: _date(): Removed features that require dateutil, which is not available under plpython3u. This includes removing the now-unused date string parameter.

mappings/VegCore-VegBIEN.csv: Removed _date/date, because _date using a string date argument is no longer supported under plpython3u (dateutil is missing). Note that PostgreSQL's own date parsing is sufficient for most dates, so this use of _date is not strictly necessary and removing it will improve import times.

schemas/py_functions.sql: Replaced xrange() with range() for plpython3u

root Makefile: Python: python-Linux: Also install python3, needed by plpython3u

schemas/py_functions.sql: Updated except clause syntax for PostgreSQL 9.1.6