refs #14 - asymmetry elimination

If consensus is not reached in suspect_timeout_ after setting install timer,
join messages are inspected and some nodes marked inactive to get rid of
asymmetry between node states.

Other:
* Collect all seen views from join messages and add to previous_views_
  in shift to S_OPERATIONAL
* Made evs consensus logging configurable via evs.debug_log_mask
* Handled one more special case when node sees user message from new
  group while in S_GATHER
* JoinMessages from nodes that have abandoned current group and formed
  new view are dropped and source nodes are marked inactive
* In gmcast forget also nodes that are marked left in V_REG stable view,
  use time_wait_/2 isolation period for partitioned nodes
Merge branch '2.x' into 3.x

Conflicts:
	gcomm/src/defaults.cpp
	gcomm/src/defaults.hpp
	gcomm/src/gmcast.cpp