xml_func.py: Use conv_items() in every XML function that needs empty (NULL) entries removed, so that they are not dependent on what process() does to the items

sql_io.py: put_table(): ignore(): Support invalid literals in addition to invalid column values. This also allows put_table() to fully support being called by put().

xml_func.py: process(): In row-based mode, if function is not explicitly a relational function but does not exist as a local XML function, treat it as a relational function. This will help in merging sql_io.put() and put_table(), since put() did not support SQL functions but put_table() does, and this ensures that a SQL function is always used if the local XML function has been removed in favor of it.

sql_io.py: put_table(): Removed into param to set a custom into table name because put_table() now has all the info it needs to generate this name automatically, and callers are no longer providing it

bin/map: by_col: db_xml.put_table() call: Use new col_defaults param to automatically set datasource_id to the in_label (datasource name)

xpath.py: path2xml(): Skip to tree created inside root, since that is how callers want to use the returned node

db_xml.py: put_table(): Import col_defaults to translate nodes to pkeys

db_xml.py: _put_table_part(): Support no in_table, for iterations with only literal values

sql_io.py: put_table(): is_literals: When ignoring all rows, return default value instead of always None

db_xml.py: put_table(): Removed parent_ids_loc and next params since these are only used in the recursion