RecipeFile class for handling XD-build recipe files

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
WIP: Manifest and Layer classes for handling XD-build manifests

Unittests must be added...

Signed-off-by: Esben Haabendal <esben@haabendal.dk>

manifest.py fixup

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
WIP: show command

Signed-off-by: Esben Haabendal <esben@haabendal.dk>