Split AKModel views into different files & introduce modular status page

Move AKModel views into several subfiles to improve overview and resolve problems with circular imports
Introduce new modular status page handling (widgets and views)
Port main status page to new structure
Move AK messages status page visualization to AKSubmission (therefore, they automatically do not show up when there is no possibility to create them)
Introduce status widget for virtual rooms
Fix timezone issue for rendering of AK messages on status page
Adapt status page URL in several views and tests