[DBClientHatohol] Change file names related with DBClientHatohol.

DBClientHatohol ->
DBTablesMonitoring

This patch only changes the file name. Class names are unchanged.
[DBClientHatohol] Rename a class.

DBClientHatohol ->
DBTablesMonitoring
Merge pull request #428 from project-hatohol/rename-db-tables-monitor-3

Rename db tables monitor 3