Add DeviceMonitoring NetJSON support

[arun1993]

As the JSON plugin in SCAL can't provide support for NetJSON schema, we can extend the SCAL APIs to any object in the form of JSON.

1. Publish NetJSON schema as different objects on the SCAL to do this. This is done as shown in the examples/json directory.
2. Or For those data-models which don't have support of the JSON plugin, we can create a ubus object and make it available at the JSON plugin by adding a new API to call and filter the ubus object.

This issue is targeted to complete by 2nd Week of August.