Configurable log fields

Added configurability for the following fields:

Date and Time: can be set to false, none, true, ganesha, local, syslog,
8601, or arbitrary string for use in strftime. False and none are equivalent.
True and Ganesha are equivalent and use the original date and time format
used by Ganesha (though generated with strftime instead of sprintf).

If both are set to local, it uses the "%c" format. Date local uses "%x",
time local uses "%X", date 8601 uses %F (2012-01-03 format), date syslog
uses "%b %e", time syslog and 8601 are equivalent to time local ("%X").

Epoch, Hostname, ProgName, PID, Thread_Name, Function_Name, Component
and Level may all be set to true or false.

Signed-off-by: Frank Filz <ffilz@us.ibm.com>