Add slashing multiplier to Validators contract, read when distributing rewards

[asaj]

Expected Behavior

Rewards are multiplied by slashing multiplier.

More specifically, the reward to the validator is multiplied by M for the corresponding account, the group share is multiplied by M for the group account, and rewards to voters are multiplied by M for the group account.

Contract Validators {
  uint256 public slashingMultiplierResetPeriod;
  function setSlashingMultiplierResetPeriod(uint256 value) external onlyOwner;

  // Resets a group’s slashing multiplier if it has been >=
  // slashingPenaltyResetPeriod since the last time the account was slashed.
  function resetSlashingMultiplier() external;

  // Only callable by the registered DoubleSigningSlasher and DowntimeSlasher
  // contracts.
  function halveSlashingMultiplier(address group) external;
}

Current Behavior

No M