sql_gen.py: Added Expr

sql.py: add_index(): Fixed bug where expressions needed to be enclosed in () to distinguish them from plain columns

sql.py: add_index(): Support simple expressions as well as columns

sql.py: Renamed index_col() to add_index() so its name isn't similar to index_cols()

sql_gen.py: FunctionCall: Removed repr() because it's a Code object and its to_str() does not take extra arguments

sql.py: run_query(): FunctionValueException: Expanded parsing to include regular function calls, not just relational functions' trigger functions. put_table(): Disabled FunctionValueException handling because this expands FunctionValueException beyond what put_table() could handle.

sql.py: put_table(): MissingCastException: Fixed bug where renaming of cast literal value was not properly propagated to the returned value of the function call, causing the query to assume that a DISTINCT ON column referred to column in one of the joined tables instead of a named column in the SELECT columns list. This logic error would have been very difficult to catch without inspecting the code!

sql_gen.py: Added wrap_in_func()

sql_gen.py: FunctionCall: Filter args through remove_col_rename() to remove any renamings from the function args

sql.py: put_table(): No handler for exception: Print full exception instead of just first line to assist in debugging