faeServer should be able to run transactions with configurable resource limits

The ability for a user to unilaterally filter transactions they deem too expensive is fundamental to the correct functioning of Fae. `faeServer` should run each transaction with a time and memory limit, whose parameters can be determined by the user. A transaction exceeding these limits should throw a special exception, possibly handled differently than other ones so as to indicate when a transaction history is "tainted" with untimely terminated code.

As a stretch goal, this limitation capability should be extended to a complete (if simple) signature server, where the local `faeServer` can accept proposed transactions requiring its signature, run them in simulation, and sign under some conditions (most obviously, that it stays within the limits).