Improved the CustomItem meta checks

[WolfyScript]

The custom checks are now 100% modular.
For each saved (and registered) CustomItem you can set so called NBT checks, that can replace the default check or extend it.

By default the CustomItem will use a single check with the key wolfyutilities:customitem_tag, which will just check for the namespaced key of the item.
There must at least one check, if you don't set one the default one is used.

To add different checks you need to configure the config of the item or add them via the API.
It uses a new field in the config called nbtChecks with a child checks, that is the actual the array that contains the checks.

"nbtChecks" : {
    "checks" : [ {
      "key" : "wolfyutilities:customitem_tag"
    } ]
  }

You are also able to code and register your own checks (inside your plugins onLoad()).
There isn't any wiki page for it you would have to look at the other checks and see how they are registered.