Added some comments of the form "// XXX: ERROR_HANDLING <explanation>"
wherever I saw a potential error but wasn't 100% sure of the intention of the code.
Fixed a few bugs along the way.
* the TxnMgr is invoked by the editor via nsRepository
* editor.h|cpp have been renamed nsEditor.h|cpp for consistency
* editorInterfaces.h|cpp have been renamed nsEditorEventListeners.c|hpp
* added nsITextEditor.h, nsTextEditor.h|cpp. The text editor is a placeholder for the rules unique to text
editing. It invokes the nsIEditor to do core editing operations.
* reworked nsIEditor and related interfaces as per emerging design.
* nsEditor::BeginTransaction and EndTransaction call nsTransactionManager::BeginBatch and EndBatch.
* added DeleteSelection to editor. Doesn't work very well yet because selection is giving me random offsets into text content.
* lots of work in the various transactions.
The key listener is now mostly a mapper of key events to editor actions. Soon, this should be 100% true.
The editor builds transactions that are themselves intelligent. The editor makes very few DOM calls itself.
It relies on the transactions to do most of the actual editing.
