Search fields can be overridden again. Fixes #709
Merge branch 'search/search-fields-overriding' of https://github.com/kaedroho/wagtail into kaedroho-search/search-fields-overriding
add clarifying comment about how test_overriding relates to model inheritance
release note for #715
Merge branch 'kaedroho-search/search-fields-overriding'