feature/new-atat

[MathiasKoch]

This PR adresses way too many issues in one, but most importantly, it marks the point from where master will be stable.

• Lock dependencies to fixed branches or commit ID
• Move to new ATAT parser, with tuple enum support, and variable compile-time calculated lengths
• Externalize socket set memory, to allow specifying static memory locations, in other ram regions
• Support DER format for SSL
• Panic-free ring-buffer with unit tests

Fixes #3
Fixes #8
Fixes #9
Fixes #13