[server][DBClientConfig] Clean up by extracting commonly used lines as a method.
[server][DBClientConfig] Clean up by removing an unnecessary intermediate object.
[server][DBClientConfig] Lift the upper restriction on a type ID of monitoring system.

On the HAPI framework, users can regist their own plugins. So it's
not reasonable to set the upper limit of the type ID.
[server][HatoholArmPluginGate] Start a plugin process.
[server][testDBClientConfig] Fix a problem in which expected lines are changed on some environment.
[server][ChildProcessWaiter] Add a new class: ChildProcessWaiter.

This class will take over the basic role of ActorCollector that
is only for collecting executed actions. This class will be used
not only for actors, but also for all the other child proesses such
as HatoholArmPlugins.
[server][ChildProcessWaiter] Rename to ChildProcessManager.

This class will not only collect (wait) child processes, but also
create them. So the previous name is inappropriate.
[server][ChildProcessManager] Add a new method: create().
[server][testChildProcessManager] Add a new test: test_createWithInvalidPath().
[server][ChildProcessManager] Fix a bug that passes an empty string when a working directory is not set.
[server][ChildProcessManager] Throw an exception to avoid Hatohol from running with storage status.
[server][testChildProcessManager] Add a new test: test_create().
[server][ChildProcessManager] Move mainThread to protected because it's not needed to be public.
[server][ChildProcessManager] Add a reset mechanism().
[server][ChildProcessManager] Add a mechanism to reap a child.
[server][testChildProcessManager] Clean up.
[server][testChildProcessManager] Fix a potential problem that may calls g_main_loop_quit() before m_loop is created.
[server][ChildProcessManager] Add a feature that can delete a EventCallback instance automatically.
[server][ChildProcessManager] Add a feature that can insert a callback when an execution is done.
[server][ChildProcessManager] Use a Doxygen's style comment.