Implement `accounts/{accountId}/staking-payouts` (#217)

* Initial impl with Big.js


Remove unused comment

Update comments and org

Update response structure

Remove validator count

* Convert to Perbill arithmetic

* Implement calc-payout crate

* eslintignore calc-payout

* Alexander feedback

* Add check for era - depth; Update openapi

* update README debug section

* Update readmes

* Apply suggestions from Joe code review

Co-authored-by: joe petrowski <[email protected]>

* add docs to payouts controller

* Clean up docs

Reverse

* Update calc/Cargo.toml

Co-authored-by: Dan Forbes <[email protected]>

* Update return property names for nominator and validator rewards

* themself -> itself

* Code style refactors and comment updates

* Small era message update

* Delete line in ReadMe

* Remove accidental add

Co-authored-by: joe petrowski <[email protected]>
Co-authored-by: Dan Forbes <[email protected]>