TODO

Several desired features are left undone or unfinished:
 
 *  port CaChannel interface to use epics.ca

 *  improve documentation, examples, unit testing.
    - document attributes for devices.

 *  add more "devices", including low-level epics records,

 *  improve wx_motor.py to be a stand-alone app with:
     - dialog window to select a set of motors for an "instrument"
     - enable "save/restore" for named positions of all motors
       in an instrument, with options to prompt-for-restore and
       prompt-for-restore-per-motor.
     - config file per instrument to allow loading a saved
       instrument definition, with saved positions
     - tabbed/notebook interface for multiple instruments.

  * more extensive thread testing