Update block processing to handle events

[shuse2]

Description

• Add event root to the block header and update the schema
• Update state machine to handle reverting of the event based on result of command execution
• Create event root at the end of block generation and block execution
  • block generation should insert the event root at result calculation step
  • block execution should verify the event root at result verification step

Acceptance Criteria

• Update state machine unit tests to check both success/fail command case
• Update consensus and generator tests for event root
• Update lisk-chain tests for new event root property
• All builds and tests must pass