Brightway2

* Add ``Activity.rp_exchange`` for easier access to reference product exchange
* ``Activity['foo']`` will now also lookup reference product classifications and properties

* Add `Database.new_node`

* Add `Database.set_geocollections`

* Change behaviour of `.get()` and `.get_activity()` to allow passing arbitrary filters and raise error if multiple results found
* Add `Activity.consumers()` and `Activity.producers()`.
* `technosphere()` no longer returns substitution exchanges by default (but still does if `include_substitution=True`); substitution exchanges are included by default in `production`.
* Add `.datapackage()` convenience method for processed datastores

* Only need geocollections for process nodes

* Can pass `Activity` objects to `get_activity`
* Add `delete_duplicate_exchanges` utility function
* Automatically add geocollections for easier regionalization setup