sql.py: put_table(): Re-enabled FunctionValueException handling, by just filtering out the value on all input columns that use the named function (since the error message does not specify which column it was that had the invalid value). This is in some ways better, anyway, because that way the invalid value is filtered out right away in all columns that could contain it, instead of potentially once for each column (if the value appears in more than one input column).

sql.py: add_index(): Fixed bug where expressions could not be converted to a string until their table name had been removed

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()