Contract modified + bug fixed

Features:
SendLines replaced with ClearLines, server generates OnPlayerAddLines if
needed
GameStatistics collected at server level and send to client when game is
finished (not yet displayed)
Bugs:
options are send to player/spectator when they connect or when options
are modified
server master is not updated in spectator mode
when a player joins a running game, opponents grid should be sent to
player
when a player joins a running game, he's not considered as playing and
then don't receive death notification
when a spectator joins a running game, opponents status (alive/dead)
should be sent to player