Also run kapt on src/main/java

We already compile Kotlin code in both src/main/kotlin and
src/main/java. But for some reason we weren't processing annotations in
src/main/java. This commit hopefully remedies that (but not tested).

Thanks to Philipp Hanslovsky for reporting.

See: https://forum.image.sc/t/29700

Author: ctrueden

pom.xml

@@ -1276,6 +1276,7 @@
 								<configuration>
 									<sourceDirs>
 										<sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
+										<sourceDir>${project.basedir}/src/main/java</sourceDir>
 									</sourceDirs>
 								</configuration>
 							</execution>