Move libuv compilation to cmake

I removed the libuv compilation script and integrated this step into cmake. There are some steps which I want to think about later:

 - download/fetch libuv from other sources (GitHub?) instead of using a subtree
 - integrate tests with CTest
 - remove the Makefile

The target should be a fully cmake driven build process, which enables us to use other tools like Ninja or Visual Studio instead of Make and a faster/parallel compilation workflow.