Merge branch 'wiki-titles' into 'develop'

src/plainui/jinja2/plainui/static_page.html.j2

src/plainui/jinja2/plainui/static_page_diff.html.j2

src/plainui/jinja2/plainui/static_page_edit.html.j2

src/plainui/jinja2/plainui/static_page_history.html.j2

src/plainui/locale/de/LC_MESSAGES/django.po

src/plainui/locale/en/LC_MESSAGES/django.po