[OE-core] [PATCH v2] wic: Add --exclude-path option to rootfs source plugin.

[Kristian Amlie]

Alright, this took a bit longer than I expected, I had to learn a bit about the
test framework in OpenEmbedded. But here is the updated patch with additional
patches enabling tests.

Two things I'm a bit unsure about: I had to add a path to the wic python script
in order to use the copyhardlinktree() function that was suggested earlier. And
I also had to modify the path in the test itself in order to use the e2ls tool
which I provided in a recipe in order to inspect the image. I hope those things
are ok.

-- 
Kristian