Allow /perbuild/visit to accept multiple tokens.

[forkiesassds]

Might need some improvements.

Closes #368.

[Goodlyay]

I don't really understand the purpose of this, but if I'm understanding correctly, then it allows multiple people to have their permissions changed at the same time? You should update the help of the commands to reflect this expansion of syntax. But it seems unnecessary to me

EDIT: I only just noticed this is addressing an existing issue, so I guess that answers my question of what the purpose is

[UnknownShadow200]

Unfortunately several issues here

• Doing just /perbuild - throws an IndexedOutOfRangeException now, instead of messaging the player You must provide a player name to blacklist.
• if (grp == null) hasErrors = true; errorCount++; is really equivalent to if (grp == null) { hasErrors = true; } errorCount++; not if (grp == null) { hasErrors = true; errorCount++; }, so errorCount will usually be incorrect
• If you provide an invalid rank name, access.SetMin/Max still gets called with group being null, therefore causing a NullReferenceException
• I'm not sure why a One or more errors occurred while executing this command. message is necessary, since the command already messages you about each invalid rank/player name
• The access.Blacklist(p, data.Rank, lvl, access.Whitelisted[0]); logic is problematic, because if you can't blacklist a whitelisted player (e.g. due to them being a higher rank), the code will just loop trying to remove that player (and failing each time), instead of moving onto the subsequent player

Not an issue with this pull request specifically, but I'm a little bit reluctant towards providing a way for someone to easily clear an entire whitelist with just -*

I apologise if this comes off as overly critical