Moved MongoClient-related classes from org.mongodb to com.mongodb.client
WIP: still need to deal with TODOs
Introduces ConnectionString into core, replacing MongoClientURI, and removing dependency on MongoClientOptions.
Moved MongoCollection and MongoDatabase and associated implementation classes from driver to driver-compat.  Removed com.mongodb.client.MongoClient, and added a getDatabase method to com.mongodb.MongoClient that returns the new MongoDatabase.
Removed com.mongodb.client.MongoClientOptions