feature(metadata): expanded metadata support

[dcvz]

Revamps metadata support to return all standard metadata received by the players. An abstraction was built around it to allow users to quickly be able to parse out common keys but also be able to handle any other non standard key.

As part of this change the old metadata events should be marked as deprecated.

NOTE: iOS also gains a method for receiving chapter metadata.

NOTE: This returns all data parsed by the players, one important thing to note is that the native players filter out non-spec/standard keys

Introduced events are:

• Event.MetatadataChapterReceived (iOS only)
• Event.MetadataTimedReceived
• Event.MetadataCommonReceived

TODO:

• iOS & Android Support
• Update example project
• Mark old event as deprecated
• Update documentation