Version 2.4.0

Introducing parameterization to the Activity Browser!

This version allows users to create and manage brightway2 parameters in the new Parameters tab. With these parameters it is now possible to craft formulas for activity exchanges, allowing users to quickly put together a parameterized system.

This release also contains the following:

• The database importer now gracefully handles a failed ecoinvent import, and in addition:
  • There is a small biosphere3 updater tool which uses brightway2-io data to add missing flows.
• Checkboxes are back and hopefully here to stay.
• Various code improvements and bugfixes.