TD canonicalization and signing

[relu91]

Among the objectives of the TD task force of this new charter are also the exploration of signing mechanisms and canonicalization, this is a tracking issue of that topic. If the TD task force ever formalizes these mechanisms we have to define user stories for Scripting API and extract requirements.

Generated from #352

[danielpeintner]

I think there are 2 relevant TD issues:

• Roundtripping TDs and consequences of TD Canonicalization wot-thing-description#1183
• Introduce a canonical TD format wot-thing-description#1023