Adding support for L3 address arbitraty mask for Ipv4

Openflowplugin currently supports only subnet masking (CIDR). It does not support Arbitrary subnet masking for L3 Source and Destination IP Address for flow match.

Example of usage of subnet mask when pushing a flow which works is as follows E.g <ipv4-destination>200.200.200.10/24</ipv4-destination>

Example of usage of arbitrary subnet mask when pushing a flow which does not work is as follows E.g <ipv4-destination>200.200.200.10/255.255.240.0</ipv4-destination> throws rest conf validation error, because current ietf-inet-types model don't support arbitrary mask.

I have a attached a file with this bug which shows the error message when we add a flow using arbitrary bit mask.

Arbitrary mask was introduced in the latest revision of ietf-yang-types (typedef dotted-quad) and that is something can be leveraged to support this addition. With its introduction, we can use both subnet mask and arbitrary bit mask.