Clean up lib dir in distribution assembly

Currently the tephra-distribution module can be used as a tephra server component, which contains the init script, configuration, and libraries.

However, one glance at the lib dir shows that it is a disaster waiting to happen, with multiple versions of the same dependencies included. (which I suspect we'd also get from the HBase classpath)

We need a way to start a tephra server with a sane classpath.

The example modules are also not neccessary for starting the server.

One way to go about it would be:

• rename tephra-distribution to tephra-server
• remove the example JARs from it
• move the assembly descriptor to the submodule
• make sure that the Hadoop and Hbase dependencies are note replicated in the /lib dir
• review or remove the license files, since we have no binary distribution