Add option for consistently sorting generated output

[marshall007]

This PR includes three major changes:

1. custom types (including enums) are now exported under the customTypes namespace, which avoids circular references in cases where a column name matches the enum name
2. adds a --order CLI option which, when enabled, sorts all exports and enum values to ensure more consistent output between runs (easier diffs)
3. adds assertEqualCode test utility method to ignore whitespace when comparing code snippets and refactors tests accordingly