CRUD ODL python RESTconf tests

* move to python2.6 and python script refactoring
* fix xml
* add CRUD tests (flow, meter, group)

https://wiki.opendaylight.org/view/OpenDaylight_OpenFlow_Plugin::Python_test_scripts

(cherry picked from commit 524344b0ad74be0fff931744aac1d1b3d3dc9999)
Signed-off-by: Michal Rehak <mirehak@cisco.com>
Change-Id: I553a7876bdfccf1cdf01a069d3c3d72bad297708