Issue 25: prvd networks command updates

[a-51-50]

Issue: #25

Solution:
When I type prvd networks -h I should see a flag listed for --public networks.
This is already there, but under list subcommand, so no changes needed.

Also, if I type prvd networks list I should see a list of all the networks currently available to me, separated by public and private.
I separated public and private networks by checking if userId and applicationId are nil, same as nchain query.

Remove prvd networks init and do not allow users to create networks.
Simply removed this subcommand.

[CLAassistant]

All committers have signed the CLA.