java.bbclass: stage all JAR files outside of ARCH related directories

java.bbclass: stage all JAR files outside of ARCH related directories

When Java things are build for more then one architecture strange things
happen:

- first architecture builds fine
- next architectures fails to build

Thats due to lack of JAR files as they were built as PACKAGE_ARCH="all"
but staged as PACKAGE_ARCH="TARGET_ARCH" so BitBake do not build them
again but Java classes are unable to find them.

Solution is to stage JAR files to non-ARCH directory. I used
staging/java for it and build tested with stable/2009 and
org.openembedded.dev branches.

Signed-off-by: Marcin Juszkiewicz <marcin@buglabs.net>