Cassandra cluster

This PR contains my work so far on creating a loadtestable picl-idp deployment.  Sorry for the size!  We have:

  - a "loadtest" directory, containing a simple loadtest hardness scripted on top of loads and loads.js
  - an "awsboxen" directory with scripts for spinning up a cluster, with:
    - one log-aggregation box running heka, kibana, etc
    - a two-node autoscaled webhead cluster
    - a three-node autoscaled cassandra cluster

@dannycoates thoughts?  I'm wondering whether this is growing a bit too big to live alongside the code, and should be factored out into a separate repo.