OO-2969: implements a maxima custom operator, add checker for the type of certain variables by import, more code to find the editor and version of the editor in manifest

OO-2969: implements process to mark question as "OpenOLAT" question that the editor can open, implements feedback based on conditions, implements unified feedback editor with condition based feedbacks, make the unknown question panel html match the runtime html markup

OO-2974: implement a way to understand different identifiers per page (classic page name, initial page name, old page names)

no-jira: add unit test for a password checker with at least 8 characters, a number, a special character, a lower and upper case character

OO-2969: find more editor and version informations by question import, desescape object data for Onyx Test

OO-2328: fix links with a servlet context, show comments in single page export, show a placeholder for videos in PDF, fix sliders javascript errors...

OO-2975: delete imported calendar after course, group and user deletion, implement a check every 10 runs to remove deprecated imported calendar, append the job to the scheduler

OO-2955: add an additional supervisor notification date field in roll call, implements some REST methods to retrieve and manipulate this data