Preparing for gcomm protocol version upgrades

EVS Join message is now fixed to protocol version 0 and the message serialization checks are relaxed so that in the future maximum supported version by the joiner can be reported in the message.

Install message is fixed to protocol version 0. In Install message generation phase maximum commonly supported protocol version is computed and it is added to Install message. When new view is installed, version information is added to View object that is propagated up the stack.

PC protocol will be fixed to same version as EVS from now on.

Unit tests for protocol upgrades, downgrades not yet supported.