create some exception for server responses

- raise CommandDisallowedError if the response is 'CommandDisallowedOnRanked' or 'CommandDisallowedOnOfficial'
- raise CommandUnknownCommandError if the response is 'UnknownCommand'
improve getServerVars and get getCvar
update version to R17
add cvar vars.ticketBleedRate

This value controls the rate of which tickets drop when the majority of control points
are held by a team (100% = normal).
Merge pull request #134 from ozon/improvements/BF4_parser

[BF4] Improvements bf4 parser