tinfoil: backport to 1.12

Backport the tinfoil wrapper that allows external utilities to make use
of bitbake code easily. This allows the OpenEmbedded layer index to
parse recipes from OE-Classic.

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