* Event logging
  * In the current API, every call is logged and certain interesting
    events are logged in the events table. I haven't implemented event
    logging yet in the new API.

* Tests
  * With Shell.py, it should be easy to write a large set of tests. I've
    thought about writing a SQLite DB backend so that MyPLC/PostgreSQL
    doesn't have to be setup in order for the tests to be run. But there
    are some technical limitations to SQLite. It would probably be best
    to run the testsuite against MyPLC for now.

* Authentication
  * Need to implement node and certificate/federation authentication.
  * Need to (re)implement "capability" (i.e. trusted host)
    authentication. Maybe implement it in the same way as node
    authentication.

* Anonymous functions
  * Implement anonymous functions for now for backward compatibility,
    but get rid of them as soon as possible

* Hierarchical layout
  * Probably need to organize the functions inside PLC/Methods/

* Deletion
  * Need to come up with a sane, consistent principal deletion policy.

* Validation
  * Need to come up with a policy (truncation? fault?) for dealing with
    variable length strings.