Fixed rxJava deprecation warnings
Added validation checks to operator constructors

JAVA-1190
Normalized CreateIndexesOperation

All other operations that use MongoNamespace have it as the first
argument.
Removing ping from public API
Make async rename collection tests more robust
Removed commented out code
Removed outdated TODOs
Removed unnecessary TODO in RequestMessage regarding requestId rollover, after testing that the server handles ids <= 0
Removed incorrect manual link
Removed TODOs after filing a JIRA for them.
Removed outdated TODO in DefaultServer
Removed TODOs in UsageTrackingInternalConnection after filing a JIRA
Removed TODO in MongoCollectionImpl due to presence of a JIRA ticket for it
Removed outdated TODO
Replaced one TODO with better javadoc, and two others with a JIRA
Added some Javadoc in org.bson
Added some javadoc for decoders
Removed TODOs after adding JIRA issues
Removed outdated TODO about limit and skip.
Removed outdated TODO