Relate file to its original entity

[cdboer]

The PROV model for commits requires files to be related to their original entity and to proclaim themselves as a specialization of that entity. Finding this original entity is already implemented, though quite slow and does not scale well with a growing amount of files. Rethink the implementation for this to be faster and more resilient. Keep an eye on performance, this shouldn't compute longer than necessary.

Right now the implementation is searching through the ever changing file paths of all files, computing tracks for each file and choosing the longest track to be the correct history of a file. Whit it bringing along a lot of computation overhead, this does not seem to be the best solution to the problem.

[cdboer]

solved in 3912f77