sql.py: delete(): Cache deletes by default

sql_io.py: put_table(): Merged remove_rows() and invalid2null() into one ignore() function that chooses the action (map to NULL or delete) depending on the value and whether NULLs have been filtered out of the column

sql_io.py: put_table(): remove_rows(): Delete the rows containing the invalid value instead of filtering them out of each select, so that the filtering can be profiled separately from the insertion. This also requires deleting rows with invalid non-NULL values instead of mapping them to NULL if NULLs have already been filtered out of the column in question.

sql_io.py: put_table(): Main insert: Don't run it inside an extra savepoint, because this will cause the creation of any helper SQL functions to be rolled back if an exception is thrown. If those functions are later re-used, the cache will think they exist when they no longer do. (Calling a function on input rows is now run in recover mode, so that it doesn't need the outer savepoint anymore.)

sql_io.py: put_table(): main_insert(): Moved code that is not part of the main query outside the function, so it wouldn't be subject to the exception handling. Preparing to insert new rows: Only do the preparation code for insert_select() if the out_table is not a function.

sql_io.py: put_table(): main_insert(): is_function: Run insert_into_pkeys() with recover=True so that errors in the function are properly rolled back

sql_io.py: put_table(): insert_into_pkeys(): Support custom query kw_args, such as recover

sql_io.py: put_table(): Use full_in_table in the into table row count assertion, since in_table may have rows deleted

sql_io.py: put_table(): Save default values for all rows in new temp table full_in_table since in_table may have rows deleted

sql.py: Added mk_delete() and delete()