Make profile specific test manifests

[skuusela]

Generate a test manifest for images by adding common tests and profile
specific tests to a manifest.

[skuusela]

@mythi Feedback? Before merging this I will have to change the way DAFT executes tests because atm it's hardcoded on using "minnowmax.iottest.manifest".

[mythi]

@skuusela this looks simple enough and OK to start with.

About the hard-coded .manifest. Now that the test-suite becomes image specific, could you simplify it and come up with some common name for a test queue manifest that DAFT uses (i.e., say manifest_name is, e.g., testplan.manifest)

Another thing we need to keep in mind but not solve right now is how Testopia comes in the picture.

[skuusela]

@mythi Rebased, made the script a bit prettier and changed the manifest_name to "image-testplan.manifest". I think this name indicates that the testplan is for the specific image.

[skuusela]

This can actually be merged as it only creates a new manifest file and shouldn't break anything.