[ConfigManager] Implement a basic part to load a configuration file.
[ConfigManager] Reduce the number of unnecessary static variables.
[ConfigManager] Add this year to the copyright.
[ConfigManager] Remove an unnecessary method call.
[ConfigManager] Add a basic framework to parse command line argument.
[ConfigManager] Add a missing g_error_free().
[DBClient] Add an option: config-db-server.
[ConfigManager] Use a ConfigManager's mechanism to check the foreground option.
[ConfigManager] Add methods: getDBServerAddress() and getDBServerPort().
[ConfigManager] Support to parse --config-db-server.
[testConfigManager] add a test: test_parseConfigServerWithPort().
[ConfigManager] Support an option: --test-mode.
[DBClientConfig] Remove the parser.

Now it's been replaced by that in ConfigManager.
[ConfigManager] Add a method: isTestMode().
[testConfigManager] Add a new test: test_parseTestModeEnabled().
[testConfigManager] Clean up.
[ConfigManager] Fix a problem that ignores --foreground option.

The reason is why the command line option cannot be gotten
before ConfigManager::reset() is called.
[ConfigManager] Remove one of the duplicated semicolons.
[ConfigManager] Rename variables to improve readability.

OptionValues ->
CommandLineOptions

g_optionValues ->
g_cmdLineOpts

optVal ->
cmdLineOpts
[ConfigManager] Revise a comment.