More w_candidate stuffs
Merge pull request #290 from NielsZeilemaker/discoveryv1.3

More w_candidate stuffs
remove walk_advice* statistics
remove walk_bootstrap* statistics
change some statistics to properties
remove WalkStatistics
fix rebase bug
change for optimize mode
simplify endpoint statistics
some cleanup
some fix for tribler
fix rebase problems
some fix
use dispersy.send_packets() instead of endpoint.send()
some fix