Remove deprecated Event data class (#123)

* [WIP] Rewrite AndroidEventBuilder to use VEvent

* [WIP] Continue

* [WIP] Rewrite Builders

* [WIP] Rewrite tests

* [WIP] Fix remaining tests (UnknownPropertiesBuilder yet not working)

* Mark EventReader as deprecated, move util method

* Update UnknownPropertiesBuilder and Processor

- Add unknownProperties() method to filter known properties
- Update test for unknown properties handling
- Refactor KNOWN_PROPERTY_NAMES to include processed properties

* AndroidEventBuilder: document how main VEvent is generated when it's missing

* Refactor EventWriter to ICalendarWriter that uses `AssociatedComponents`

* Remove Event class

* - Add @WillNotClose annotation to Reader and Writer parameters
- Deprecate AndroidEvent2 class
- Make AndroidEvent2 values public

* Refactor AndroidEvent2 deprecation message

- Update deprecation message to suggest using Entity / EventAndExceptions instead.

* Minor fix

Author: rfc2822