NFD

In NFD configuration file general section, add configuration option(s) for RouterName.

This issue contains:

• determine whether to declare one configuration option, or multiple configuration options
• decide the name and syntax of configuration option(s)
• determine the behavior upon a configuration reload signal
• develop GeneralConfigurationSection class to replace functions in nfd::general namespace (to avoid conflict in ndnSIM, no global variable is permitted)

Documentation and NFD Developer Guide should be updated as part of this issue.