use correct case for classes, closes #1233

app/controllers/calendar/single.php

app/controllers/course/enrolment.php

app/controllers/course/lvgselector.php

app/controllers/course/studygroup.php

app/controllers/ical.php

app/controllers/messages.php

app/controllers/oer/mymaterial.php

app/controllers/studiengaenge/informationen.php

app/routes/Events.php

app/views/blubber/compose.php

app/views/my_studygroups/_course.php

...ews/studiengaenge/studiengaenge/stgteil_bezeichnungen.php

app/views/studiengaenge/studiengaenge/studiengangteile.php

db/migrations/1.155_tic_5170_clean_up.php

db/migrations/1.156_tic_5204_add_datafield_type.php

lib/calendar/CalendarWriterICalendar.class.php

lib/classes/FilesSearch/Result.php

lib/classes/ForumAbo.php

lib/classes/JsonApi/Routes/Events/UserEventsIcal.php

lib/classes/JsonApi/Routes/Events/UserEventsIndex.php