Signed-off-by: Luke Kanies <luke@madstop.com>

This commit adds a Request instance into the indirection,
pushing it all the way to the terminus instances.  It's
a big commit because it requires modifying every terminus class.

There are still some thorny design issues.  In particular, who
should be responsible for making the request object?  I've tried
having both the indirection class and the Indirector module creating
it, and both have their issues.

Also, the Catalog class previously allowed passing Node instances
directly to the find method, which is now no longer possible because
the Request class would treat the node as the instance being found.
We need the request class to have two modes, one when it's passed an
instance and one when it's passed a key.

to Indirection#destroy.

Previously, for example, the configuration terminus that was a
subclass of 'code' would have been stored at
lib/puppet/indirector/code/configuration and would have had
to have been named 'configuration'.  Now, the subclass
can be named however the author prefers, and it must be stored
at lib/puppet/indirector/configuration/<name>.rb, where <name>
is the name you've chosen for the terminus type.  The name only
matters insomuch as it is used to load the file from disk and
find the appropriate class when asked.

The additional restriction is that the class constant for the terminus
type must have its name as the last word, and the indirection must
be the second to last word.  Thus, in our example, we can choose
any class constant that ends with Configuration::Code; given that
there's only one Configuration class at this point, it makes the
most sense to define the class as Puppet::Node::Configuration::Code.

This is somewhat awkward, because of the class's location on disk,
but the only other real option is to autogenerate a
Puppet::Indirector::Configuration class constant, which is, I think,
uglier.