Add examples of C, C++ and Fortran hosts linking PCMSolver

[robertodr]

We should show more explicitly how a host program can link against PCMSolver. We assume that the host uses CMake, but that's not always the case.
We have the C_host and Fortran_host test cases and it is easy to piece out what the link line for both should be, but adding an explicit example (possibly a separate repository) and more explicit documentation would certainly be helpful.
As much as I don't like Makefile-s it would be a good idea to write a couple of those in these examples.