Lazy payout (#346)

* fix: avoid using substrate native name

* update: adjust RING/DOT ratio

* update: better error info

* update: sign prefix

* update: accuracy

* update: claims list

* remove: migration tests

* add: session

* fix: tests

* fix: RING/DOT ratio

* add: session

* update: lazy payout

* update: deps

* todo: tests

* update: resolve deps, #347

* update: deps

* update: set default history depth to 14 days