added under score under the section title to remove a warning.
added a new Hatohol server REST Server API manul page: overview.

The implementation has not been started yet. This commit just defines
the specification of the API.

Note: This commit is a part of work to solve the issue #9.
https://github.com/project-hatohol/hatohol/issues/9
extended the specification of response of overview RESET API.

In this fixed version, the responsed status such as number of hosts,
items, and triggers are summarized by each monitoring system.
added members to tell information about bad servers to the response definition of the overview REST API.
added monitoring server information such as name and IP address to the definition of the response of overview REST API.
implemented a basic structure to response 'overview' REST request.

Many members in the response are still stub. I will add code to
set them after this.
defined a structure for information of a monitoring target host.
added a new method: DBClientHatohol::getHostInfoList().
Fix UserName and PassWord hard-coded
added a new test: test_getHostInfoList() for DBClientHatohol::getHostInfoList().
extended DBClientHatohol::getHostInfoList() to get the hosts that belong to a certain monitoring server.
implemented a feature to provide the number of hosts in a server via overview REST request.
added a comment.
extended DBClientHatohol::getItemInfoList() only to get items of the specified server.
implemented a feature to provide the number of items in a server via overview REST request.
Fix scope of constructor & desctructor of UnifiedDataStore
extended DBClientHatohol::getTriggerInfoList() only to get triggers of the specified server.
implemented a feature to provide the number of triggers in a server via overview REST request.
added a framework to provide system status and host status via overview REST servervice.

Note: The implementation to get number of hosts is still stub.
extracted code to setup the DB for trigger test as setupTestTriggerDB() to use it from other functions.