go-kosu: make init a subcommand instead of a flag

[hrharder]

Overview

Makes --init a subcommand instead of a flag.

For example to start a node:

• Before:

  # does both -- sometimes not wanted if we need to update config prior to start
  kosud --init

• After:

  # initializes home dir
  kosud init
  
  # start the node
  kosud

Rationale

There are cases where we want to initialize our directory (generate config and private keys) before we start the node. In the current implementation, the node can only be initialized if it is also started at the same time.

This way, we can generate our keys and config, and then update our config before we start the node. An example would be when setting up a production validator, we need to generate our keys and config before we start the node to set up the proper sentry infrastructure.

Notes

• Also add some aliases for other flags