conf: Add `general.router-dead-interval` configuration setting

refs: #1878

Change-Id: I21f2837118cda424904e0b0e60708a12deeabc8e
sync: Avoid use of boost::serialization::null_deleter

Refs: #2072

Change-Id: Ie860c2d09d38025750be056d03d71b5de58f1c5b