Convince oasis to build and install a so indirection

I also changed the findlib name to be all lowercase to match findlib convention. There are no collisions as the other zmq libs use "ZMQ" and "lwt-zmq".

Also, I would recommend to change the repository/project name to "ocaml-zeromq" to fit the convention that other ocaml libraries and bindings use.

I tested this oasis file with zmq 2.2.0 after commenting out the zmq_ctx_new reference and it worked in both the toplevel and standalone bytecode and native compilations. Let me know if it doesn't work for you.