base host name and ditaa updates

- Updated the code that generates the base-host-name.  This is used to
  load host-specific files.  I found that in some cases my Mac's
  hostname was not exactly as I has set it in the sharing prefs.  It
  would occasional have a dash and a number appended to the base host
  name.
- Updated the logic used to override the default path to the ditaa.jar
  file required to render ditaa code blocks