Rework webApi queries

[KkevinLi]

This PR refactors the webapi query code which allows us to chain filters + pass in eventTypes.

Before we were only able to do firebaseWebApi.database().ref(path).orderByKey().on("value", onValueEvent") but now we can do firebaseWebApi.database().ref(path).orderByKey().equalTo("value).on("child_added", onValueEvent)

The api calls are backwards compatible, but now calling on() will not fire your callback for every event change at that path. Before on() listens to value and child changes whereas now it listens only for the given eventType.

[KkevinLi]

I've updated the code so that it more strictly follows the Firebase Web API (To test you can copy paste examples from https://firebase.google.com/docs/database/admin/retrieve-data)

Breaking Change:

• To handle errors you MUST pass in an onErrorEvent callback. (onValueEvent will not have a result.error to check for any more. A DataSnapshot is returned which follows the docs)
• To listen for child_added, child_removed, child_changed, child_moved you must pass in that event type (See updated docs). Before we listen to all at once which led to multiple duplicate calls.

Branch also includes:

• Remove short imports as they are deprecated in Nativescript 5.2.0 +
• Fix some types where values can be undefined
• Update to database transaction document
• Removed DataSnapshot.ref() as it's did not return a web DataSnapshots.ref(). (Still a TODO)
• Add firebase.database.servervalue.timestamp

[KkevinLi]

Any update on this PR? Is there something I need to change before this gets pulled in?

[EddyVerbruggen]

Oh man.. ehm.. probably not, but I'm struggling to find time to review it.