PEP8 for project.py
Refactoring path order for clarity
PEP8
Lowering the tolerance in file_info_cache.py

The tolerance for the last modified date was 0.5 seconds before. This is
too slow to be detected mainly in fast running test. Now it is 0.1
seconds.
Annotating and PEP8.
Temporary renamed the adjoint sources test.

Some changes for the adjoint source calculation did not get reflected in
the tests. They are now temporarily disabled until a suitable solution
is found.
Rewrote the test_utils.py tests to use pytest.

This is done as a test to see how it works. Seems to work nicely.
Started to work on project tests.