First-call timing instrument

```
Much of Caliper is focused on measuring performance in long-running processes.
I'd like for us to also support measuring startup performance.

I've got some slow code that appears to perform well on microbenchmarks. The
internal implementation of this code looks like this:

private static X cached;

public static X get() {
if (cached != null) {
return cached;
}
return cached = compute();
}

private static X compute() { ... }

Even if I cleared the static cache, it isn't appropriate to do multiple
measurements in one VM because I need the measurement to include class loading
time.

I'd like an instrument that forks a VM for each measurement taken. It would
make a single time() call and exit the forked VM.
```

Original issue reported on code.google.com by `jessewil...@google.com` on 28 Mar 2011 at 6:22