GitLab

According to
https://github.com/3MFConsortium/spec_production/blob/1.1.2/3MF%20Production%20Extension.md#chapter-1-overview-of-additions
random UUIDs, i.e. version 4, are valid for lib3mf.

Thus, this commits removes the dependecy of libuuid in favor of a
hand-crafted implementation of uuid v4.