sql.py: put_table(): Added is_func param for whether out_table is the name of a SQL function, not a table

db_xml.py: put_table(): Treat every node name that starts with "_" as a function, not just members of put_table_special_funcs. This ensures that DB function args are always treated as values, not children with fkeys to parent.

bin/map: by_col: Strip only XML functions that are not in the DB

db_xml.py: put_table(): Make special_funcs externally available as module constant put_table_special_funcs

sql.py: tables(): Changed schema param to schema_like and filter the schema using LIKE so that all schemas can be selected

to_do/timeline.doc: Updated to reflect the month we spent on optimization and column-based import

sql.py: put_table(): in_table name: Remove '-pkeys' suffix from the into table name before adding '-input' so that the name is shorter and clearer

sql.py: put_table(): Wrap repr() calls for debug messages in strings.as_tt() to add Redmine formatting

sql.py: put_table(): Output "Adding index" debug message with level=2.5 so it's not part of the Redmine steps

schemas/vegbien.sql, functions.sql: Cast functions: Fixed bug where invalid value exceptions were not being caught, because implicit conversions to the return type apparently only happen outside the block containing the RETURN statement (i.e. at the end of the function). Fixed by adding explicit type conversion to return type, so that type conversion would happen inside try block.