Make ERR_YOUREBANNEDCREEP differentiate between local and global bans

[examknow]

It's always bugged me how the ERR_YOUREBANNEDCREEP reject message begins with You are banned from this server implying that the ban only applies only to that specific server even if the ban was global. I think we should use a different message for global bans (i.e. You are banned from this network or You are banned from $networkname) or even allow this to be customized by the network like on InspIRCd.

[dwfreed]

Local bans will eventually stop being a thing, and all bans will be global, so differentiating them doesn't really seem like a good use of effort. Changing the numeric's message to use "network" or the configured network name would be alright, but I feel like making it fully customizable would be less useful, since clients may choose not to show your message at all.