* refactors function based report views into class based for EIV, OEK, EMA, KOM
* introduces BaseReportView for proper inheritance of shared logic
* refactors generating of qr codes into proper class
* extends 404 template (user should check the URL)
* introduces new decorator "uuid_required" which performs a check on a given 'uuid' or 'id' parameter
* throws a Http404 exception --> redirect to 404 template instead of 500 error template
