Add flag and question for creating credentials file

• Add -c|--credentials as a flag to the init command to create the credentials file
  • Takes an optional path, default to $HOME/.bbctl/credentials.yaml
  • Require 1 or more --credentials-entry that takes a json string {"uri": "example.dso.mil", "username": "john_doe", "password": "$EXAMPLE_DSO_MIL_PASS"}
• Add a question to the interactive command
  • Ask if they want to create a credentials file
  • Ask for a file path, default to $HOME/.bbctl/credentials.yaml
  • Require they enter one or more credentials entry
    • Ask for a uri
    • Ask for a username
    • Ask for a password
• In both cases write the yaml file to the path given

  credentials:
  - uri: "example1.dso.mil"
    username: "John_Doe"
    password: "***********"
  - uri: "example2.dso.mil"
    username: "johndoe"
    password: "***********"