add chef-server-redhat template

Initial stab at a RHEL variant of the chef-server bootstrap template. I've only tested on CentOS (and thusly this only supports CentOS). 

Items of note:
* This installs chef-server via gems as RPMs currently lag behind their Debian counterparts. * * The `chef-server` cookbook in its released form doesn't provide a way to set webui attributes so the webui is not completely configured.