Proposals v2. Discussion system. Iteration5

[shamil-gadelshin]

Features:

• spam-gate: max allowed post count in a row
• modification of the post and thread author authentication
• discussion events

Work to do after the Rome-release:

• create a monorepo
• stake fixes: Fix stake module and allow slashing and unstaking in the same block. #161
• change origins and include membership and council actors: Map Substrate origin parameter to the MemberId and CouncillorId in the proposals module #174
• discussions - two write access modes:
  a) open: any member can write.
  b) closed: only author, the current council (which may change at any time), and other specially added members can post.
• stake modification: to store an account_id to perform an unstake to (modify StakingEventHandler)
• move engine and discussion modules to decl_error approach (after the substrate update)
• provide an implementation of the T::ThreadAuthorId in the codex call of the discussion create_thread() (remove temporary stub)

[shamil-gadelshin]

Will be reworked during iteration 6.