Validate block hash and signatures

[JekaMas]

It's a first iteration fixing our consensus and voting.

When I had added proposed block and block fragments validation, the consensus crushed, panicked and crushed. So I had to make many changes until it started work better.

Main changes:

• fixed double choosing a proposer in each round
• fixed votingSystem algorithm
• fixed bug with starting validator.Start twice, that was caused incorrect voting, a part of Merkle proof errors and all duplicate vote errors.
• force some wait after proposal block sent to prevent a data race. If proposer announced a block it switches to PreVote stage that only 100ms, at the same time all other validators have to wait up too ProposalTimeout (>400ms), so it can happen that the proposer will fail with VoteTimeout constantly
• validating a proposal block and block fragments: restored a correct block sign, checking block number and hash, checking validator's round and chainID
• removed data race between receiving a proposal announce and block fragments
• removed a data race related to events.Post
• check voters addresses in voting_table while checking for duplicated votes
• refactored client/core/voting_table_test.go to remove shared state between tests and data races
• fixed stateDB panic when more than one restore revision was called
• In client/knode/validator/validator.go val.round is always 0: init -> val.round = 0, newRoundState -> if val.round != 0 -> val.round++. It causes that a part of init doesn't work and votingSystem always gets round=0 (causes duplicate votes). So added a proper round change and inits.

Cons:

• crush-recovery doesn't work fine.

Closes #787 #91

Next steps are in #837

[yourheropaul]

Why did you remove this?

[jmatosp]

maybe we could check ctx timeout and break the func being a loop

[JekaMas]

The check is a few lines below the code fragment :)

[jmatosp]

why not our normal log.Crit with context

[jmatosp]

not sure if you need this, the votes could be replaced by AddressVote?

[yourheropaul]

On the local cluster, I get errors like

WARN [10-22|12:36:11.066] Majority of validators pre-voted nil
WARN [10-22|12:36:11.292] got a proposal block add error           err="expected proposed block round 33, got 44" block="\n\tProposal(969333d451f6cc2a35a298d94bc5d425b04e2eb90a877de797133
3ffaed6acf7)\n\tBlock Number:\t\t69\n\tRound:\t  \t\t\t44\n\tLocked Block:\t\t0000000000000000000000000000000000000000000000000000000000000000\n\tLocked Round:\t\t0\n\tV:        \t\t\t0x2
8\n\tR:        \t\t\t0xbabea431231c85c8c130f6661c727c7895168fc2e1fe491557385e88c82842ac\n\tS:        \t\t\t0x3a2119e7492f8e8f6168c66e2d39b15801f097443fc89d00c5917ab661be3b63\n\tHex:
\t\t\tf88a452c80a00000000000000000000000000000000000000000000000000000000000000000e201a0000000000000000000000000000000000000000000000000000000000000000028a0babea431231c85c8c130f6661c727c7
895168fc2e1fe491557385e88c82842aca03a2119e7492f8e8f6168c66e2d39b15801f097443fc89d00c5917ab661be3b63\n"
WARN [10-22|12:36:12.678] Proposal's block is nil, voting nil      block=true