Feature: Language query parameter for Calendar requests

[JorgePBrown]

Add a query parameter for calendar requests that determines in what language the properties should be.

The possible languages should specified in the documentation. More specifically in events.md or some document that is about the API in general and not about a specific resource or resources.

What should be done if some properties aren't in the wanted language? The options I see are:

• Send in whatever language is available
• 404