Changes to List account balances

changed the pattern of the query request parameter account.balance from ^((gte?|lte?|eq|ne)\:)?\d{1,10}$ to ^((gte?|lte?|eq|ne)\:)?\d{1,19}$

the response property _status/messages/items/data became nullable for the status 400

the response property _status/messages/items/detail became nullable for the status 400

the response property balances/items/account became nullable for the status 200

the response property balances/items/tokens/items/token_id became nullable for the status 200

the response property links/next became nullable for the status 200

the response property timestamp became nullable for the status 200