Lower resources for single

- alphabetizes keys in charmconf
- consolidates charmconf template rendering into utils

- adds worker_multiplier to reduce # of processes launched on various services, most of which end up on the main controller kvm: glance, keystone, and nova-cloud-controller. The default in the charms is currently 2, and we set it to 1 for the single install case.

- bump RAM in controller kvm to 6 GiB

the last two bullets mean this fixes #300
Should we look into doing customizable constraints as well?