Make user module also able to delete users

[Itxaka]

delete_entities module is kind of complex for this task as it requires everything to be filled:

       delete_entities:
       -  path: /etc/passwd
          entity: |
                  kind: "user"
                  username: "foo"
                  password: "pass"
                  uid: 0
                  gid: 0
                  info: "Foo!"
                  homedir: "/home/foo"
                  shell: "/bin/bash"

We could have the user module have an extra key called delete: bool which in turns instead of creating the user, uses the given info to find the user and remove it instead, so it makes it easy to add/remove users