Display flash message in page header if message available

Signed-off-by: JWhy <jwhy@jwhy.de>
Add item detail page view, update app.css to add margin to item thumbnail

Signed-off-by: JWhy <jwhy@jwhy.de>
Move items controller out of admin context, add item detail page to controller

Signed-off-by: JWhy <jwhy@jwhy.de>