act2 migration

[MrChico]

As I'm getting closer to being able to output k specs from act2, I'm thinking about how to integrate it to the klab workflow. Roughly, we want to replace klab build with act compile, and there is some experimentation going on on the act2 branch of this repo.

In this process, I expect the following things to change:

• I'm not convinced having the calls section as part of the behaviour is a good idea. I think better would be to simply indicate the dependencies of specs in the config.json for each directory, to get the gas extraction and proving workflow from that.
• Obviously, there are syntactic changes to how specs are written, which in general will make many specs a lot shorter.
• Instead of a separate storage markdown file, the new act format works with a spec for the constructor. From this both storage locations and type checking can be inferred.