converted to static pages, folder src/stati/error_pages

src/plainui/jinja2/plainui/403.html

src/plainui/jinja2/plainui/404.html

src/plainui/jinja2/plainui/500.html

src/plainui/static/error_pages/403.html

src/plainui/static/error_pages/403_FORBIDDEN.jpg

src/plainui/static/error_pages/404.html

src/plainui/static/error_pages/404_NOT_FOUND.jpg

src/plainui/static/error_pages/500.html

src/plainui/static/error_pages/500_INTERNAL_SERVER_ERROR.jpg