Attestation mechanism: SGX DCAP

[g2flyer]

• precondition for Generalize attestation support #15 to really be useful
• simplifies install procedure as there is now a debian repo which automatically updates the base packages and includes a driver which uses dkms to auto-rebuild on kernel upgrades. (Alas, last time i've checked, the sdk itself was still not yet a debian packages and is required even for just running FPC iff you want to use simulation mode. This means also changing our docu from just pointing to SGX SDK source and more explicitly mention install options. See the corresponding change in PDO as a starting point