Make VariableParser use an instance to allow for state information.

VariableParser now needs to store information about custom types (specifically
enumerations).  Thus make parseVariable take an instance now by making it
a method of VariableParser again.  Also change the TET to use a global
singleton (called TET) to store the TET's VariableParser (since the type
information is global to Matlab).

git-svn-id: https://groke.mcmaster.ca/svn/grad/colin/branches/TableTool_javization@11082 57e6efec-57d4-0310-aeb1-a6c144bb1a8b