Added a default filter for observer messages.

Also created a an alias property for Hive names, the hiverole. For convenience.
Code review mode. Removed redundant functions for killing in Villager class.

These functions are more suited for the hive construct. Also, we need a way
for the hive members to check the current leading consensus for their hive (if
any). We might have to introduce gevent here sooner or later.