Add gpgmepp

Since gpgme cannot be built with C++ and Qt bindings for MSVC due to lack of support in their build system, I wrote a patch that adds CMake build system for the C++ and Qt bindings. The binding libraries are built on top of the existing C gpgme library. I tried introducing CMake builds for gpgme as well, but it turned out to be near impossible. For this reason this is a standalone blueprint rather than an extension to the current gpgme blueprint.

The patch also contains various small changes to gpgme++/qgpgme to make it MSVC-compatible. Most of this could be eventually upstreamed.