[BF3] implement Client.state property

 Client.state returns whether the player is alive or not
add isAlive method for easy usage (e.g. in plugins)

 Client.isAlive() returns true or false
remove param player_name (client have all what we need)
change unnecessary comment to help description
handle IndexError
change description comment
[BF3] client.state implementation
Merge branch 'features/bf3_client.state' into origin-release-1.10