Add Honeycomb interface management tests (ipv4, ipv6, ethernet, routing)

 - add test cases for managing ipv4, ipv6, ethernet and routing
 configuration on VPP interface
 - add keywords used in these tests to set and verify configuration
 - add method and vat template for dumping an interface's
configured IP addresses
 - add method for converting between ipv4 netmasks and
   network prefixes
 - clean up documentation of older Honeycomb keywords

Note: Test cases are tagged with a placeholder tag to allow manual
test runs locally. It should be replaced with the appropriate
environment tags once Honeycomb service is deployed on virl.

Change-Id: I99ce1e72c8550f520f8c35ef4a93eaebb530db78
Signed-off-by: selias <samelias@cisco.com>
Signed-off-by: Matej Klotton <mklotton@cisco.com>