Allow role paths to be appended on the command line

##### Issue Type:

Feature Pull Request

##### Ansible Version:

ansible 1.7 (devel d4548fdd01) last updated 2014/07/18 11:25:37 (GMT +1000)

##### Environment:

N/A

##### Summary:
Allow role paths to be appended on the command line

Move the DEFAULT_ROLE_PATH handling into bin/ansible-playbook and just pass roles_paths to playbooks (the plays pick up the path from the playbook)

Usage:
```
ansible-playbook -r /opt/local/ansible/common/roles -r /opt/local/ansible/application/roles playbook.yml
```

Still respects the defaults and settings in ansible configuration file.

##### Steps To Reproduce:

N/A

##### Expected Results:

N/A

##### Actual Results:

N/A