Upgrade core library version 0.82.3 -> 0.83.0

**Includes https://github.com/realm/realm-cocoa/pull/887**

This release of the core library makes some changes in the query API. For further details, see https://github.com/Tightdb/tightdb/blob/master/release_notes.md#0830-release-notes.

I have updated CHANGELOG.txt, but I have only added this:

> Updating to core library version 0.83.0

I'll let you guys decide on what additional details to add.