Add support for userlists

[pieterlexis]

This commit allows adding userlists if both formats via ansible.

Example vars:

haproxy_userlists:
  - name: 'MyList'
    users: 
      - name: 'user1'
        password: 'insecure-password user1'
      - name: 'user2'
        password: 'insecure-password user2'

[PierrePaul]

Really cool. Thank you!