Add support for enumerated types into the parser and collection.

VariableParser now deals with enumerated types correctly, and VariableCollection
exposes the enumerated types as appropriately so that further parsing/generating
will work correctly.

git-svn-id: https://groke.mcmaster.ca/svn/grad/colin/branches/TableTool_javization@11087 57e6efec-57d4-0310-aeb1-a6c144bb1a8b