What was MODE, containing the execution mode of the daemon (EXEC, PAUSE, etc)
is now called OP.  The MODE channel is now used for the mutually exclusive
behavioral modes of the daemon:

EXEC
MANAGED
MANUAL

The independent MANAGED channel is removed.
The MANAGED MODE option can not be selected directly, but is instead set
by setting the MANAGER to be a valid string.

Screens and tests are updated appropriately.

git-svn-id: https://redoubt.ligo-wa.caltech.edu/svn/guardian/trunk@1282 e3bfa956-ff0e-4416-9af7-00b7a258cde5