Connector moves and renames

[ricellis]

Renames to allow for other endpoints in future (we'll get the cloudant part from the package name):

• CloudantSourceConnector -> ChangesSourceConnector
• CloudantSinkConnector -> ChangesSinkConnector

Put the "public" content in these packages
com.ibm.cloud.cloudant.kafka.connect.connectors (for the *SourceConnector and *SinkConnector classes)
com.ibm.cloud.cloudant.kafka.connect.transforms (for the transforms)
com.ibm.cloud.cloudant.kafka.connect.transforms.predicates (for the predicates)

Put the other content in a sensible set of sub-packages in
com.ibm.cloud.cloudant.kafka.connect.internal

[mojito317]

As we discussed offline earlier: CloudantSinkConnector should not be renamed.