Make cs-diff/grouping to compare files under lp dir, instead of work directory

[marcosps]

It would make things easier to detect when we need different branches for the code. The way things are being done today is cumbersome because the LP developer needs to know which codestreams require which externalization method.

Once this is changed, we can know for sure how many branches we need, since the code in the lp/ directory will also contain the externalization method used, making it different only on the codestreams that do it differently.

This of course means that klp-ccp should also improve it's code output, but that's somebody else's issue.