Upgrade Derby dependency to 10.14.2.0 (released in May 2018). Note that the 10.14 series are the last versions compatible with JDK 8; next Derby versions will require JDK 9.
In preparation for JDK 9, we should also declare explicit dependency to Derby in pom.xml files with Maven test scope. Current Apache SIS relies on JavaDB bundled with JDK 6, 7 and 8, but JavaDB is no longer bundled with JDK 9 and above. Apache SIS will continue to check if JavaDB is available in the JDK home directory (until we migrate to Java 9), but this will no longer be a documented feature.