Getting started documentation needs to add derbytools to the client classpath

The client driver now lives in derbytools.jar. Our documentation needs to say that the client-side classpath needs derbytools.jar. See for instance http://db.apache.org/derby/docs/10.15/getstart/twwdactivity4.html It is likely that other examples need to be updated.

This issue was raised in the following derby-user email thread: http://apache-database.10148.n7.nabble.com/I-don-t-find-the-JDBC-driver-class-in-derbyclient-jar-td151132.html