[Checkins] [zopefoundation/Products.ZCatalog] 10566f: Add new `getAllBrains` method to the ZCatalog.

[GitHub]

  Branch: refs/heads/add-get-all-brains
  Home:   https://github.com/zopefoundation/Products.ZCatalog
  Commit: 10566ff897d5193b920d691770fe624b7cfc38c6
      https://github.com/zopefoundation/Products.ZCatalog/commit/10566ff897d5193b920d691770fe624b7cfc38c6
  Author: Hanno Schlichting <hanno at hannosch.eu>
  Date:   2017-11-30 (Thu, 30 Nov 2017)

  Changed paths:
    M CHANGES.rst
    M src/Products/ZCatalog/ZCatalog.py
    M src/Products/ZCatalog/tests/test_catalog.py
    M src/Products/ZCatalog/tests/test_zcatalog.py

  Log Message:
  -----------
  Add new `getAllBrains` method to the ZCatalog.

The method returns a generator of brains for all cataloged objects.
You can use this if you relied on `searchResults` returning all brains
for empty queries before version 4.0a2.

Also add tests for the catalog's `__getitem__` and `clear` methods.