Separate namespaces

[jagot]

We need to ensure all modules have distinct names, since multiple modules with the same name is undefined behaviour according to the Fortran standard, and leads to confusion in general. My suggestion is to prefix all modules which belong to a specific program by the name of the program, e.g. av_energy_expression -> dbsr_mchf_av_energy_expression, &c. Similarly, there is significant overlap between versions 3 and 4, and here I suggest we suffix all modules by the version number.

[jagot]

Another big advantage to this, is that we can then properly support efficient, parallel builds using Ninja, which requires that all Fortran modules have distinct names.