xml_func.py: process(): Refactored to emphasize special handling for row-based and column-based modes. In row-based mode, always use a DB relational function over a local XML function when possible, to faciliate testing of DB relational functions in row-based mode. (The shadowed local XML version will still be tested in non-DB modes, such as outputting to intermediate XML files.)

bin/map: Move retrieval of out_db's relational functions outside of process_input() so they can also be used by the non-by_col case

bin/map: out_is_db: Don't evaluate relational functions in xml_func.process() because these will be evaluated by db_xml.put()

xml_func.py: Removed no longer used strip()

bin/map: Use xml_func.process(..., strip=True) instead of xml_func.strip()

xml_func.py: process(): Added strip()'s functionality via strip option

schemas/functions.sql: Added _merge relational function

schemas/functions.sql: Added join_strs() aggregate

sql.py: Renamed index_pkey() to add_pkey() to be consistent with add_index()

sql.py: into_table_name(): In function args, omit column name for function result columns