Lab

Lab
* Reports: round values to desired precision before determining colors (Jendrik Seipp).
* Restructure and extend documentation (Jendrik Seipp).
* For developers: run CI tests on Ubuntu 20.04 in addition to 18.04 (Jendrik Seipp).

Downward Lab
* Allow adding SAS+ files with ``FastDownwardExperiment.add_suite()`` (Jendrik Seipp).

Lab
* Take float precision into account when highlighting table cells (Jendrik Seipp).
* Allow serializing `pathlib.Path` objects into JSON files (Jendrik Seipp).
* For developers: add ``.github/CONTRIBUTING.md`` file (Jendrik Seipp).
* For developers: separate tests for Singularity and FF example experiments from other tests (Jendrik Seipp).
* For developers: skip ``cached_revision`` doctests if ``DOWNWARD_REVISION_CACHE`` variable is not set (Jendrik Seipp).
* For developers: use f-strings in code (Jendrik Seipp).

Downward Lab
* Print number of tasks above and below separator lines in scatter plots (Jendrik Seipp).
* Ignore tasks for which runs have been filtered out in aggregate reports (Jendrik Seipp).
* Fix order of bracketed task counts per domain in table reports (Jendrik Seipp).
* Gracefully handle empty scatter plots (Jendrik Seipp).
* Make ``score_*`` attributes absolute, i.e., include tasks for which not all algorithms
have a value in aggregations (Jendrik Seipp).

Lab
* Bump minimum Python version to 3.6.
* Move ``CachedRevision`` from ``downward`` to ``lab`` package (Thomas Keller).
Please note that the interface to the class is experimental and may change
in the future. Feedback is welcome!
* Let tests fail if any example experiment produces unexplained errors.

Downward Lab
* No changes.

Lab
* Sort numbers with suffixes (5K, 2M, 8G) and "infinity" correctly in tables.
* Gracefully handle missing "info" or "summary" tables in HTML reports.
* Abort if a function is passed to a ``filter_*`` kwarg.
* Abort if a filter checks missing attribute names
(e.g., when passing ``filter_algorithms`` instead of ``filter_algorithm``).

Downward Lab
* Add example experiment for running Singularity planner images.

Lab
* Use newer txt2tags version and remove bundled copy.
* Call parsers with active Python interpreter.
* Don't call deprecated ``time.clock()`` (removed in Python 3.8).
* Don't add Lab to ``PYTHONPATH`` in ``BaselSlurmEnvironment``.

Downward Lab
* Revision cache: only delete "misc" and "experiments" dirs if they exist (Maximilian Fickert).

Lab
* Format source code with black (https://github.com/psf/black).
* Fix filters: retrieve new run ID from modified runs (Silvan Sievers).

Downward Lab
* Remove call to ``rm -f output.sas``. Newer Fast Downward versions remove the temporary file
automatically. If you want to keep the file, add ``"--keep-sas-file"`` to the ``driver_options``.
* Fix ScatterPlotReport: skip None values in `max()` computation (Silvan Sievers).
* Fix ScatterPlotReport: place diagonal line correctly even if axis scales differ.