Made observation navigation text shorter.
Download error handler will now catch all errors instead of just those 
with errno EACCES or ECONNREFUSED.  EACCES still get handled by a 
prompt to get a new CADC certificate.  Any other error is displayed with
the option to retry the download.
Merge pull request #196 from drusk/navview_tweak

Observation navigation text tweak
Merge pull request #197 from drusk/download_errorhandling

Download error handler catch all errors