added code to include ItemID in a message on ItemDataException.

The previous commit causes ItemDataException due to operation
(comparision) between inappriate types. So this patch add
code to include each ItemID on the message.

The message is like below.

[ERR] <AsuraThreadBase.cc:72> Got Asura Exception: <ItemData.h:242> Undefined operation: '==' between String and Unsigned (ItemID: 104 and 122)

<< Tasks to do in the near future >>
- investigate the reason why string and unsigned is compared
  on an inner join.
- make tests for ArmZabbixAPI.
- clean up of VirtualDataStoreZabbix, DataStoreZabbix, and
  ArmZabbixAPI.
- parse arguments of --data-store-zabbix and create multiple
  DataStoreZabbix instances.