Harden the dev environment against 'vagrant halt' calls.
This change adds a new Upstart script to start the Perforce server on startup and
copies the P4PHP library to a static location so that Apache can properly load the
module at boot time. Vagrant sets up the shared directories well after all of the
services have been initialized which was causing Apache and Perforce grief.
Also tweak a couple parts of the readme to clarify some of the odd Vagrant behavior.
Many thanks to DJ for his help with testing the dev tools.