Add all the supported photon-selections to bg_from() method.
Add more BT -> leakage conversion in test_burstlib.py
Add complete test coverage for bg_from() method.
Use a config file to find FRETBursts folder.

Add Installation notebook to install the configuration file.
More BT -> leakage conversion in multi-spot notebook
Tests: use HDF5 format for multi-spot tests
Tests: fix test errors
Fix bug in bg_from() found by unit-testing
Tests: add complete coverage for .iter_ph_times() method