Update tooling in tools/clientconf/ to create, modify, and print ClientConf values.

[jmwample]

As an extension to PR #62 this seeks to extend the customization tools for creating ClientConfs. I am exporting this to a separate issue to get the original PR merged.

[jmwample]

Design proposal:

• remove the hard-coded subnet specification in the tools/clientconfig/clientconfig.go file.
• add a --subnet-file option that takes a path to a TOML file, parses it into a PhantomSubnetsList (see struct defined by protobuf). Once parsed replace the current subnet list for the config that is being operated upon.
• add options to manually add / modify or delete elements of the subnet list. These can be similar to the current options that exist for the decoy list.
  • This may require adding numbers to the subnet printing system so that modify and delete can reference the correct element of the subnet list.
  • May require some way to specify both the weight and the subnet list of the element being added.

The station has a semi-related process for parsing subnet lists from a toml file. However this parses and tracks multiple generations and has some issues with types that we shouldn't have to deal with here. We just need one PhantomSubnetsList defined in the file.