Implement TOSCA Topology Template

The topology template is recognized with a keyword topology_template. The main ingredients of the topology template are node templates representing components of the application and relationship templates representing links between the components. These elements are defined in the nested node_templates section and the nested relationship_templates sections, respectively. Furthermore, a topology template allows for defining input parameters, output parameters as well as grouping of node templates....Please refer to the spec for more detail (provided in Appendix A under title "Topology Template definition" )