bitbake: tinfoil: implement server-side recipe parsing

bitbake: tinfoil: implement server-side recipe parsing

It's not really practical for us to parse recipes on the client side, we
need to do it on the server because that's where we have the full python
environment (including any "pure" python functions defined in classes).
Thus, add some functions to tinfoil do this including a few shortcut
functions.

(Bitbake rev: 8f635815d191c9d848a92d51fdbf5e9fd3da1727)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>