added 3 party events

[reyaleman]

Pull Request Prelude

• I have followed proper The Forgotten Server code styling.
• I have read and understood the contribution guidelines before making this PR.
• I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

Added 3 party events

• Party.onInvite(self, player)
• Party.onRevokeInvitation(self, player)
• Party.onPassLeadership(self, player)

Issues addressed:

[MillhioreBT]

I like onInvite, makes a lot of sense.
However the other two methods, mmmm are not very consistent.
I don't see valid reasons to use them.

Deny a player to revoke an invitation? because?
Deny one player passing the leadership to another? because?

Suppose I return false in the Party.onPassLeadership event then I can't make anyone else a leader anymore, but if the leader dies or the player gets kicked off the server what happens? rule is violated, leadership now belongs to the next member...

I think my mind is very closed right now, so I hope you can show some good examples to learn a bit about how to use these two methods.

[Tofame]

@MillhioreBT deny...? Are those only for denying, or are those to run a script when something is happening e.g. when inviting.
If the latter then those could be useful for writing some otclient modules.