add Panorama 5.1 (same as 5.0) for set cli
add 5.1 to doc also for set cli
add PAN-OS 6.0 XPaths for set CLI
I am developing with Python 3.3 by default now so add as supported.
type=user-id does not have an action parameter; remove commented action=set
Rewrite XML response message parser to use xml.etree.ElementTree
path/xpath to match each known format.  This will make it easier to
support additional messages formats.

Multi-line messages (multiple line elements) are now newline
delimited.
operation command 'show jobs id nn' can have response with path
'./result/job/details/line'; if so set status_detail to text (can
be multi-line).

example:

  $ panxapi.py -t pa-200 -Xo 'show jobs id "402"'
  op: success: Configuration committed successfully
if an XML response message is an empty string set it to None vs. ''
Merge branch 'master' of https://github.com/kevinsteves/pan-python into wildfire