Adding ability to group preferences, and to add a description in each generated tab, only compatible with BS4

search bar text always white when not focused

WIP #2

WIP #2

Adding credits in footer
printing warnings only once
WIP #2

Showing the form by default (can be overridden)
WIP #2

Allowing to use simple_message_page with its context

Using Django's lost password workflow, using app templates, adding quick start indication and example in the test project