adds ical input to calendar html templates and implements data handling

- the icalHandler in the backend is used in two instances. First, when
  the user adds a new ical calendar into the database, routes.py passes
  the information (name and url) to the ical Handler. The calendars are
  saved in the database as type 'ical'.

  Then, when a connected device pulls current events, all the calendars
  which are of type 'ical' are pulled and parsed for current events.
  See the backend commit for details on what happens there.

- All google Calendar related functions now have an additional check,
  to make sure that the calendar they are working on is of type 'Google'.

docker/calendarwatch/Dockerfile

@@ -2,7 +2,7 @@ FROM python:3.8-slim-buster
 RUN apt-get update && apt-get upgrade
 RUN pip3 install flask Flask-SQLAlchemy flask_migrate flask_login flask_wtf python-dotenv
 RUN apt-get install gcc libpcre3 libpcre3-dev libmariadbclient-dev -y
-RUN pip3 install uwsgi email-validator RandomWords icalevents
+RUN pip3 install uwsgi email-validator RandomWords ics
 RUN pip3 install google google-oauth google-auth-oauthlib google-api-python-client mysqlclient
 COPY docker-entrypoint.sh /usr/local/bin/
 EXPOSE 8084