Add SSH key generation at bootup

This pull adds a script that starts on bootup and pre-generates an SSH key for the student machine. This is primarily used so the student does not need to run puppet twice to get their SSH key added to the master for the Fundamentals git workflow.

This has not been tested when creating a new VM, but I did take a clean existing one and re-apply the site.pp prior to installing PE on an agent and master and testing the workflow. It does indeed result in only two Puppet runs - once to configure ~/puppetcode on the student, and once to initialize the new environment from storeconfigs on the master.