Watches a directory (or filesystem), update info to EPICS PVs, and send an email when the space drops below a threshold.

 *   browse the project: https://subversion.xor.aps.anl.gov/trac/bcdaext/browser/epicsdf
 *   documentation: http://subversion.xray.aps.anl.gov/admin_bcdaext/epicsdf
 *   checkout: {{{svn co https://subversion.xor.aps.anl.gov/bcdaext/epicsdf ./epicsdf}}}