More Editor Cleanup Continued:
 - Fixed "addRom()" routine.  The tree is now properly built from the vector of TableTreeNodes.
 - Fixed "Close Image" worker.
 - SetUserLevelWorker became much simpler.  It now is just a rebuild of the JTree.
 - RomTreeRootNode.java now is just a basic DefaultMutableTreeNode.
 - Closing a Rom now properly cleans up memory.
Note: lastSelectedRom will not be set when focusing on a TableFrame.  This feature requires unnecessary work and/or references.  lastSelectedRom will now only be set when selecting something in Rom tree.