Ant script which assembles signed jars and simulates OSGi.

A typical setup when developing OSGi bundles is to have unit tests
placed in a jar separated from the main code. The jar is loaded by the
same class loader as the parent. They are called fragments. This scripts
simulates this environment by producing separate jars, loaded by the
same class loader at test runtime.

Signed-off-by: Gunnar Wagenknecht <gunnar@wagenknecht.org>