Convert erlangsp + coop to a single library with src/erlangsp.app.src

Rebar requires the *.app.src file to be at the top level of src or ebin. Instead of having a coop.app.src and an erlangsp.app.src, they were combined into a single top-level app.src and left as a library rather than an application.

To make this work and still retain src/coop and src/erlangsp, the rebar.config was changed to specifically identify include directories for each of the sub-projects.