Adding code to create new webserver

* Including updated Varnish role to install Varnish on webservers
Fixing groups
Using NVM install of node instead of apt
Updating orchestration vars and helper file locations
Updates to templates, common tasks and the webserver

* Updating mongoserver playbook and vars to add replSetName var

* Removing unnecessary webserver templates

* Updating webserver playbook to fix nova integration
Merge pull request #8 from DoSomething/common-webserver

Common tasks, webserver and mongo playbook changes.