Long descriptions are cut during ics import

[ulbrich-media]

Hey, while using the ics importer in one of our projects I encountered an issue. All descriptions where cut if they where a bit longer. I was able to reduce the error to the ICal Library/Script used by the extension right here, where there already is a comment indicating that there is no multiline support.

Since the current ICS-Parser was abandoned, I replaced it with the still maintained u01jmg3/ics-parser.

I also had issues with timezones being wrong after import, but I didn't follow that problem since it was solved with the new library.

@georgringer if you want I can gladly provide a PR with the implementation of the new library. However there are one or two properties I deactivated during import since I have no clue what they do, so a second opinion or some testing would be appreciated.

Replacing the old Parser may also resolves issue #18.