[Docs] Clarify role development cycle
[Docs] Clarify role development cycle

Role development and maturity cycle had many issues:
- The development had duplicate content
- The maturity cycle was not described

This commit clarifies the rules that apply to the roles.

Change-Id: Iffc79c34e52528366b7c998d502024d5231e3144

yanyao/openstack-ansible,stackforge/os-ansible-deployment,cfarquhar/openstack-ansible,openstack/openstack-ansible,bunchc/openstack-ansible,stackforge/os-ansible-deployment,yanyao/openstack-ansible,bunchc/openstack-ansible,openstack/openstack-ansible,cfarquhar/openstack-ansible