- IDiDriver becomes IDi.IDriver (logical consequence of previous move
from IDiClient to IDi, if we are to be consistent)
- IDi.terminate() dispensed with: now specify that deployer must
unbind() after use. Thus, we get a simpler API and impl'n--terminate() is
a little onerous--in exchange for having to terminate resources every
time we explicitly unbind().
- IDi: void bindOrReturn() becomes boolean bindIfAvailable()