Update formats.py and repository_tool.py.

repository_tool.targets.delegate_hashed_bins():

Edit comments, add logging information, and rename 'max_number_of_bins' (now 'total_hash_prefixes') for clarity.
Fix expected value of 'number_of_bins' (power of 2 instead of multiple of 16.)
Remove the 'self' argument in get_filepaths_in_directory() (now a staticmethod.)

formats.py:
NUMBINS_SCHEMA may now start from 1 (allow the creation of 1 delegated hashed bin.)
Refactor test_replay_attack.py.

Refactored to use the 'unittest' module (test conditions in code, rather
than verifying text output), use pre-generated repository files, and
discontinue use of the old repository tools. Expanded comments.
Merge pull request #199 from vladimir-v-diaz/refactor_test_replay_attack

Refactor test_replay_attack.py