Brightway2

* Remove `fasteners` and write locks
* Remove `docopt` and `bw2-uptodate.py`
* Substitute `platformdirs` for `appdirs`
* Remove `psutil` dependency

* Yanked due to insufficient testing and documentation

* Add `Exchanges.to_dataframe`

* [PR 109: Export edges and activities to dataframes](https://github.com/brightway-lca/brightway2-data/pull/109)
* [PR 105: Complete revamp of IO Table functionality](https://github.com/brightway-lca/brightway2-data/pull/105)
* [PR 104: Fix `Exchange.lca()`](https://github.com/brightway-lca/brightway2-data/pull/104)
* [Fix 95](https://github.com/brightway-lca/brightway2-data/issues/95)
* [Moved `wurst` extraction functions to `bw2data`](https://github.com/brightway-lca/brightway2-data/commit/55f107177ead8a73cdf88a5b5be56bf6811bf27f)

* Fix and test export CSV metadata from databases during datapackage creation

* Improve lookup of activity classifications and properties