Similar to VariableParser, also make MatlabParser a single static method.

Since MatlabParser has no reason to have an instance of it managed by a
user, just make it use a single static method to access its functionality.
Overall it makes code simpler (avoiding the nasty getRootExpression call).

git-svn-id: https://groke.mcmaster.ca/svn/grad/colin/branches/TableTool_javization@10847 57e6efec-57d4-0310-aeb1-a6c144bb1a8b