Update tests to changes in TestTools interface (and minor fixes)

Update tests to changes in TestTools interface

To check what was changed in TestTools see description of test-tools!100 (merged).

• node.get_block_log() -> node.block_log.
• tt.BlockLog(None, path, include_index=False) -> tt.BlockLog(path).
• Updates Hive submodule to hive!731 (merged) (to get changes from TestTools).

Minor fixes

• Remove unused import.
• Remove unneeded block_log.artifacts stored in repository (should be only a block_log).
• Changes in generate_block_log.py:
  • Remove block_log.artifacts generated by generate_block_log.py script.
  • Add log about finished block log generation.
  • Ignore directory generated by script.
• Accesses to block log with path relative to current working directory (directory, where script were run) were replaced with path relative to script file. So now it doesn't depend where user is and runs the script. Output is generated always in the same place.
• Uses of os module were replaced with pathlib.

Requires: hive!731 (merged)

Please review: @kmochocki @mzebrak