Merge branch 'devel-2.5'

* devel-2.5:
  rapi.client.ModifyNode should PUT rather than POST
  Fix RAPI node modify client and server calls
  xen: changes to facilitate "xl" support (xen 4.1)
  xen: abstract instance config file naming
  Abstract xen's 'xm' command as a constant
  Fix RAPI documentation build
  rapi: Allow auto-promotion on node role change
  rapi: Add resource for modifying node
  opcodes: Add comment to *SetParams result description

Conflicts:
	lib/rapi/client.py
              - both functions stay, remove one empty line
	lib/rapi/rlib2.py
              - convert new function to 2.6 rapi style
	test/ganeti.rapi.client_unittest.py
              - both tests stay, trivial

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>