USECASE: Add support to validate network state using csv tables

[dmulyalin]

Extend salt-nornir to validate network using data from csv table. Probably need to code support in TestsProcessor and/or create runner nr.test

For example, assuming we have this csv data:

host,interface,admin_state,line_state
R1,Eth1/1,up,up
R2,Gi0/0/0,down,down

Take above and compare with devices state and produce test results.

NAPALM has similar functionality by comparing getters output with expected output, but it accepts data in dictionary format, which might not scale well compared to csv - csv spreadsheet are easier to edit by humans as well as many systems provide export of data in csv format, allowing to extract desired state tables from them.

Another example, assuming this bgp peers table:

host,peer_ip,state
R123,10.1.2.3,established
R321,10.3.2.1,admindown

take output from devices and verify network state.

In essence, this feature will allow to define desired state of the network using tabulated data expressed in csv format. Optionally, can add support for markdown and its tables