NLSR

This should be a command line option to nlsrc advertise/withdraw as to whether to save/remove from nlsr.conf advertising section.

Some limitations with this patch.
1. It removes all the comments from the conf file. It's because I am using BOOST to read and write to the conf file, BOOST removes the comments in that process.
2. Once a prefix is advertised without a save command, it cannot be saved later.
3. Once a prefix is withdrawn without a delete command, it will not be deleted from the conf file.

Above limitations has been resolved.

Additionally,

few StatusCodes are introduced in NLSR.

406: Prefix is already saved or deleted from the configuration file.

205: Saving or deleting a prefix from the configuration file. This also includes saving or deleting an already advertised or withdrawn prefix from the configuration file.

StatusCode loosely follows the HTTP semantics described in RFC2616 section 10 (RFC2616)

Ehm... Yes, config files should be static and it is quite unexpected if they are modified... If you need modifiable state, it should go under /var area. On some systems, this /var area can be different and is managed by the system appropriately.