xml_dom.py: NodeTextEntryIter: Allow empty values through as None, and instead filter them out in TextEntryOnlyIter using new helper function non_empty(). This allows XML functions to decide for themselves whether empty values should be filtered out, because process() will now no longer automatically remove them. This will enable process() to work with SQL functions, which must not have empty values filtered out because this will remove required, but nullable, arguments.

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