atol, rtol per file

[domeniconappo]

Current version of comparator defines atol/rtol and then compare entire dirs using same values of tolerance.

We need to add:

1. atol rtol at compare_files level
   In this case, user can't use compare_dirs method and has to write his own script to walk through dirs and change atol/rtol depending on his requirements per file basis

2. a dynamic way of defining atol/rtol based on min/max/avg/any-other-indicator-that-helps values from one of the maps