a proper replacement for PremiumVanish

In the recent past, we had used PremiumVanish as our vanish plugin for staff. This plugin offered many benefits over Essentials vanish, which we are currently using.

Primarily, the features missing from Essentials vanish are:
- Staff could toggle their ability to pick up items when vanished
- Containers could be opened and manipulated silently
- Staff would be reminded that they are in vanish with an actionbar message
- Staff would receive permanent night vision while in vanish mode
- Using a special server IP would cause the staff member to join vanished

We will likely not use PremiumVanish again, but rather opt to reimplement these missing features ourselves as part of a custom moderation utilities plugin.