Adds support for dot-delimited petname paths to the CLI
`eval` command. This required modifications to the `evaluate`
method of the daemon's `host.js`, and the introduction of a
new formula type, `lookup`, modeled on the `web-bundle`
formula. Also adds a unit test for this behavior.

The `lookup` formula type is necessary because the names
in a lookup path may have neither petnames nor formula
identifiers associated with them. Consider:

```text
> endo eval '10' --name ten
10
> endo eval 'foo' foo:INFO.ten.source
10
```

The only way retrieve the value for `source` is to call
`E(HOST).lookup('INFO', 'ten', 'source')`, and since the `eval`
formula expects its values to be mediated by formula identifiers,
the lookup of `INFO.ten.source` must itself be stored as
a formula.

Lookup formulas must be associated with the namespace for
which the pet name path is valid. In practice, this means
an object with a variadic `lookup()` method. Previously, these
objects were referred to as "agents", but in the future, not
all such object will be agents (i.e. guests or hosts). Therefore,
here we replace all references to "agent" with "hub", short
for "naming hub".