Implement reward estimations for staking a validator

[ManuGowda]

Description

Enable users to estimate the rewards while staking.

Motivation

As a network participant I want to stake tokens for a validator "validator 1", the wallet should provide an ability to get the expected reward for a daily, monthly and yearly.

Additional Information

• getExpectedValidatorRewards in the dynamic reward module, gives expected reward for a validator for several cases (day, month, year)
• getExpectedSharedRewards( in the pos module gives the expected shared reward if staking a validator with a particular amount.

To achieve the estimations:

• call getExpectedValidatorRewards(validator1.address), and expected daily/monthly/yearly reward

• then call pos.getExpectedSharedRewards(validator1.address, daily/monthly/yearly, myStake = 500) and this gives my expected shared reward

• Also enable users to sort validators by Validator weight, Commission, Rank