Assume version "1.0" as default (if version is not specified) for configuration files

[manrodrigues]

During pktvisor load of config file, if version is missing than don't error but instead assume 1.0

https://github.com/ns1labs/pktvisor/blob/develop/cmd/pktvisord/main.cpp#L186

Motivation:

If pktvisor is provisioned via configuration file, the user must inform the "version" :

version: "1.0"

If the version is not informed, pktvisor will fail.

Consequently, the orb-agent also fails:

https://app.zenhub.com/files/340174841/b7da00d3-393e-4c80-b6f2-b5a6230508ad/download

In order of make the experience easier, we could set version: "1.0" as default (if version is not specified).