sql_gen.py: ColDict: Only allow dict inputs to constructor so update() can later be used. Ensure keys_table is a Table object.

sql_gen.py: ColDict: Translate NULL values to the key column's actual default value. This avoids incorrectly comparing against NULL in join/filter conditions when the column's actual default value must be used.

sql.py: DbConn: Added col_default()

sql_gen.py: ColDict: Take a db param for later use in getting default column values

sql_gen.py: ColDict: Take a keys_table param for operations that require the output table. Use this to convert all string keys to sql_gen.Col objects.

sql.py: put(): Use a sql_gen.ColDict for row, just like in put_table(), so that put() will benefit from planned enhancements to sql_gen.ColDict, such as translating NULL to the default value of a NOT NULL column

schemas/functions.sql: _nullIf: Fixed bug where NOT NULL parameters were not supported, because an input NULL value would not match an existing DEFAULT value in a select query, by temporarily disabling _nullIf until this can be supported. Removed previous workarounds.

bin/map: out_is_db, row-based mode: Disabled using DB relational functions instead of XML functions because they were causing problems

sql.py: put(): DuplicateKeyException: Fixed bug where select() call needs to be surrounded by value_or_none(), not value(), because sometimes there is no entry

schemas/functions.sql: Added indexes on all relational function parameters since the unique index will not be used for lookups