Validator queries validator info for given validator address.

Validator defines a validator, together with the total amount of the Validator's bond shares and their exchange rate to coins. Slashing results in a decrease in the exchange rate, allowing correct calculation of future undelegations without iterating over delegators. When coins are delegated to this validator, the validator is credited with a delegation whose number of bond shares is based on the amount of coins delegated divided by the current exchange rate. Voting power can be calculated as total bonded shares multiplied by exchange rate.