Fix for joins code block
DOCS Setting allowed_extensions in YAML

3.1 compatible docs in place of #3267
Merge pull request #3308 from camfindlay/patch-9

DOCS Setting allowed_extensions in YAML
API Let extensions control folder selector in HtmlEditorField_Toolbar
Merge pull request #3312 from tractorcow/pulls/3.1/extend-htmleditor-parentid

API Let extensions control folder selector in HtmlEditorField_Toolbar
Merge pull request #3277 from kopymark/patch-3

Fix for joins code block