[Toaster] [RFC] build to toaster fixes

[Michael Wood]

I've been working on a number of fixes to make sure that the build and 
layer information is stored correctly in toaster.

There is quite a bit of stuff needed to fix this more fully and 
definitely scope for refactoring - I've left in old code paths as I 
don't think the full extent of how the information is handled can be 
fully tested without a large suite of unit tests.

Branch is at 'michaelw/toaster/build-recognition-fixes' on poky-contrib. 
I've had good results in testing building core-image-* on the fido release.

Michael