Prototype multiple commodity support

Updated the backend to support multiple commodities on the balance report.
Only showing first (0th in array) on the front end at the moment.
Updated readme with plan for progress. Time to try getting price
history...
Milestone planning

Updated readme with milestone planing for phase 2. Milestone 1 has been
carved out.
Updated the balance report front end to display all balances per account
instead of just the first.