Add a few iCalendar properties

[tcitworld]

• Status, which matches to string
• Categories, which matches to a list of strings
• Class, which matches to string
• Comment, which is a simple text field
• Geo, which maps to a tuple with latitude and longitude

[lpil]

Thanks @tcitworld, this is great. Left some comments :)

[tcitworld]

Fixed :)

[lpil]

Published a new version, thanks!

[tcitworld]

thank you