Encapsulating state object members

Full encapsulation of account_recovery_request_object and change_recovery_account_request_object, some members of account_object also made private. Members rearranged to reduce size, also unused account_object::reset_account removed and proxy changed to id (unfortunately there are some problems with changing other similar members to id - comments added).

[Note] change in account_object::proxy influences order in response from database_api::list_accounts(by_proxy), also proxy given in call must exist.