v0.6.0

This is an interim release, after some major refactoring, and before we add the automatic gain selection and refactored container classes. It's not intended yet for production.

Some Major changes since last release:

• new EventSource class hierarchy for reading event data, which now supports simulation and testbench data from multiple camera prototypes (notably CHEC, SST-1M, NectarCam)
• new EventSeeker class for (inefficient) random event access.
• a much improved Factory class
• re-organized event data structure (still evolving) - all scripts not in ctapipe must be changed to work with the new data items that were re-named (a migration guide will be given in the 0.7 release)
• better HDF5 table output, supporting merging multiple Containers into a single output table
• improvements to Muon analysis, and the muon example script
• improvements to the calibration classes
• big improvements to the Instrument classes
• lots of cleanups and bug fixes
• much more...