Numeric and timestamp fixes.

Several bug fixes.

• Column type is now compared on alter column matches, so you can change data type.
• Column types timestamp and timestamptz are now aliases to the longer postgresql names timestamp without time zone and timestamp with time zone. It will now only update when changed instead of every run.
• Numeric types are now parsed from the HCL source, loaded in the PSQL source, and compared in the column match logic.
• Program exit code is non-zero on failure.