Install the agent lib to non arch specific directory

https://fedorahosted.org/fesco/ticket/961
Update the spec file

- install the agent to /usr/lib/abrt-java-connector on all arches
  because Java does not officially support multilib

- do not require a particular java devel package because the agent works
  with the most common Java versions (1.6, 1.7, 1.8)

Thanks Mikolaj Izdebski and Jiri Vanek!

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Update README