Add FuseSoC support

Created by: wallento

Hi, this is a draft PR that adds FuseSoC support. Before merging we need:

• Upstream fpnew core file, ideally in its own repository. That also removes the dependency to clone the repo at a particular path. Before this can happen, we need a minor fix to FuseSoC for include path handling (@olofk is working on it)
• Support for the core simulation (working on it right now)
• Support for synthesis targets if people agree thats a good way to move forward. A lot of things could be adopted from the ibex repository, that did some groundbreaking improvements to FuseSoC and use many of the features.

Cheers, Stefan