Add caching for Path, BGPPath, IP and Prefix structures (#218)

* Add caches

* Replace IPs and Prefixes with pointers to these

* Fix nil pointer derefs

* Fix nil pointer deref

* Fix community encoding

* Fix tests

* Fix tests

* Fix tests

* Fix tests

* Fix tests

* Fix tests

* Fix BGP path hashing

* Fix path attr decoding

* Fix tests

* Fix tests

* Fix tests

* Fix tests

* Cleanup

* Cleanup

* Revert config change

* Fix Benchmark. Fix ClusterList PA.

* Fix ClusterList tests

* Add client

* Remove stale test

* Cleanup

* Increase verbosity on decode failure

* Improve chache layer performance

* Improve bgp path cache performance

* Cleanup