Extend get_order_book API to return more info

PR for #2637 and https://github.com/blocksights/blocksights-open-explorer/issues/9.

This PR adds 4 data fields into the order struct:

id - ID of the limit order
owner_id - owner account ID of the limit order
owner_name - owner account name of the limit order
expiration - expiration time of the limit order

The full order struct becomes:

   struct order
   {
      string                     price;
      string                     quote;
      string                     base;
      limit_order_id_type        id;
      account_id_type            owner_id;
      string                     owner_name;
      time_point_sec             expiration;
   };

The order_book struct itself is unchanged.

   struct order_book
   {
     string                      base;
     string                      quote;
     vector< order >             bids;
     vector< order >             asks;
   };

bitshares / bitshares-core

Extend get_order_book API to return more info #2638