I tested it this out and I believe this would work for you:
1. In Calibre, open Preferences
2. In Preferences, choose Adding Books (in the Import/export section)
3. In Adding Books, uncheck "Read metadata from file contents rather than file name"
4. In the "Configure metadata from filename box", there is a drop down menu under Regular expression. Choose (?P<title>.+)
5. Click Apply, close Preferences and you are done.
Note: if you want to test it out before saving the change, use the Test box where you type in a sample of a file name (e.g. Melville, Herman - Moby Dick.rtf). When you click test, you will see how Calibre would process the filename. After the change, there is an option to restore the default settings, if you need to do so.
Good luck!
