Parties megaissue

[thedax]

I'm breaking this off from the larger social system issue, since parties have several issues and missing features:

• Bonus stat stuff is not yet implemented, but this is fairly low priority since we don't have combat and stats are more or less a suggestion than a reality right now
• No support for teleport sharing yet

To-do:

• Refactor all party-related code to send an Option<u64> to the global server when checking for a party instead of party id 0
• Refactor all party creation-related code not to use random ids, we should use one source (each, not one for both) of truth for chatchannel ids and party ids that increments every time, like ClientIds do

The following issues have been resolved:

• Registering for content finder while in a party won't enlist the entire party and may potentially cause panics, I haven't tested it as leader yet
• When anyone goes offline, they're removed from the party, or if the leader goes offline, the party is auto-disbanded, instead of sending a member offline/member returned notification.
• When the leader leaves the party, it's auto-disbanded instead of auto-designating a new leader
• Strategy Board is not sharable with your party
• No support yet for waymark presets beyond sending a blank one to clear all waymarks.
• Existing target signs/markers are now sent to people changing zones or returning from being offline.
• Existing waymarks are now sent to people changing areas or returning from being offline.
• Party members don't show up on the minimap yet, likely due to an unknown opcode that seems to be sent to the client around every 5 seconds when in a party, but this needs more research and is low-ish priority. The unknown opcode was UpdatePartyPositions, a segment sent around every 5 seconds that broadcasts the party members' positions to everyone else to keep things in sync. It's used for at least the minimap and riding pillion on mounts.
• Inviting a player to your party doesn't show a log message, and it was caused by the zone init flag being set to CROSS_WORLD, because you typically cannot form parties in duties.
• Ready checks are not yet supported