Start of DAL implementation, independent of the database

Add dal2.HttpStubDAO and impl for MongoDB that hides logic of building
queries to Database.

Added a DSL that lets describe an action sequence and then  generates
scalatest, executing it and markdown files containing curl commands
for these actions.

Actualize docs

Release v3.10.0

Enable initialization of tracing context (fix #70)

Properly render JsonResponse in schema

Support header values for state search (fixes #51)

Release 3.8.0

Support body for any http verb

Improve behavior of JsonOptic.set (fixes #13)

Release v3.7.0