Fix build process to include JAR libs in WAR file again

JAR files required for a Forrest-built webapp to run are no longer copied to the build hierarchy as announced by Nicola Ken on Jan 26. The WAR archives created by "forrest war" therefore don't contain these required libs anymore and can't be deployed out of the box.

A possible fix for this issue is to have src/core/targets/war.xml include the core and optional JARs directly from ${forrest.home}, using the Ant War task.