Refactor settings

fixes https://github.com/bitpay/copay/issues/1113
fixes https://github.com/bitpay/copay/issues/1203
fixes https://github.com/bitpay/copay/issues/1290
fixes https://github.com/bitpay/copay/issues/1208
fixes https://github.com/bitpay/copay/issues/864
fixes https://github.com/bitpay/copay/issues/1024
fixes https://github.com/bitpay/copay/issues/1022
fixes https://github.com/bitpay/copay/issues/1081