Feature #913

Updated by Alexander Watzinger over 2 years ago

Implement functionality for changing the uploading a custom logo:

* if no custom logo is set or available the default one is used
* a file select an upload form displaying available files, allowed extension, size limit, max height and width
* a database entry in web.settings with name "logo_image_id" "custom_logo" and the value "logo." + extension e.g. "logo.jpg"
* when uploaded the file is saved in static/images/custom as "logo." + extension
* before uploading a new one the old one has to be deleted

Options how to deal with size (especially height) to don't break layout:

resize in browser (quick solution but display quality might suffer)
* resize in backend (would need an extra library e.g. python3-pil)
* don't allow upload of bigger images (for that the image has to be first uploaded, checked and than delete)