xpath.py: Added is_all()

xml_func.py: process(): List out the xml_dom.NodeElemIter iterator so that it won't be affected by concurrent changes to the DOM tree

xml_func.py: process(): Merging children: Support merging non-adjacent children by using new xml_dom.merge_same_name(). This should eliminate the need to sort children of the same name next to each other in the mappings so that they will be merged.

xml_dom.py: Added merge_same_name()

bin/map: ex_tracker: Don't add row_ct to iters count in column-based import (by_col) because errors are not done by row, so a % of rows affected is not meaningful

sql_io.py: put_table(): NullValueException: Missing mapping for NOT NULL column: Raise error if there is no default input column to fill in the rows with. Missing mappings for required columns are a normal circumstance with path mappings (plantname, namedplace) because the mappings include intervening levels that may not be specified by the datasource. These mappings have default input columns for the intervening levels, so for them, this will continue to not be flagged as an error.

sql.py: index_cols(): Fixed bug where index columns were sorted by their position in the table, not their position in the index. This was causing the order of columns in covering indexes not to match their order in the corresponding output table index, preventing merge joins and slowing down joins because of the need to do a seq scan. Refactored to use pg_get_indexdef() on each column position index and parsing the result with parse_expr_col(), which greatly simplifies the query and automatically provides the correct sort order.

sql.py: Added parse_expr_col()

sql_gen.py: Added unesc_name()

sql.py: index_cols(): Removed unneeded table param, since the index name is unique within its schema. (The schema is looked up in the search_path if needed, by using ::regclass.)