Throw exception when the user tried to do things that aren't supported

Hi!

Thank you for this library. It would be nice if things that aren't yet implemented could throw an exception stating that they are not yet implemented.

An example: When I try to fetch a log object from a v1.4 WITSML server, then after getting the data successfully on this line (https://github.com/hashmapinc/witsml-client/blob/dev/src/main/java/com/hashmapinc/tempus/witsml/client/Client.java#L296), no parsing is done because `convertVersion` (https://github.com/hashmapinc/witsml-client/blob/dev/src/main/java/com/hashmapinc/tempus/witsml/client/Client.java#L726) does not support 1.4. Rather I end up on this line (https://github.com/hashmapinc/witsml-client/blob/dev/src/main/java/com/hashmapinc/tempus/witsml/client/Client.java#L298) and am returned `null`. It would be much better for me as a user to be notified of the fact that this is not yet supported. :)

Thanks!