Fix random startup issues with the TET.

Sometimes when starting up, a previous handle would clash with an existing
handle, causing the TET to fail to load and locking Matlab into a state
where it can no longer exit.  Fix by ensuring on load no previous handle
is ever used, and instead just regenerate all of them.

git-svn-id: https://groke.mcmaster.ca/svn/grad/colin/trunk/TableTool@10858 57e6efec-57d4-0310-aeb1-a6c144bb1a8b