(CFACT-133) Implement querying into structured facts from command line.

Implementing querying into structured facts from the command line.
This is necessary as we move to more structured facts in the output.

The syntax is using a dot notation.  Examples are:

cfacter networking
cfacter networking.ip
cfacter networking.interfaces
cfacter networking.interfaces.en0.ip
cfacter processors.models.2

Array values treat each element as a named index.  Arrays that contain
arrays or hashes can also be accessed:

cfacter foo.0.foo # first element is a hash (get "foo" element)
cfacter foo.1.0   # second element is an array (get first element)
auto const& on a char? I wonder what that looks like when you compile it.