[New Handler] Google Calendar

[tahpot]

Add support for syncing Google Calendar data.

Required scopes:

• https://www.googleapis.com/auth/calendar.readonly
• https://www.googleapis.com/auth/calendar.events.readonly

API docs:

https://developers.google.com/calendar/api/guides/overview

Will require creation of new schemas:

• calendar
• event

[tahpot]

Dupe of #94