prepared ical import
Merge branch 'master' into icalimport

Conflicts:
	index.php
	templates/overview.php
Merge branch 'master' into icalimport
started to implement ical parsing
moved from array iteration to stack operation
prepared readTimezone
working on implementation of importIcal
preparing reading events from vcalendar
coded some further parsing
Merge branch 'master' into icalimport
working on deduplication, preparing for hashing: moved ical-formatting
of event to appointment class
completed importing functions, debugging follows
added some lines of code to comply with own output ;)
at this point, we ar able to import from calcifer and opencloudcal.
bug fixin, polishing some functions
added importing of urls
converted "already present"-output to warning
added translation
added data flow chart
preparing for calculation of UTC times