Using Enmap.multi

To account for people that might use a large number of enmaps in the same project, I've created a new `multi()` method that can be used to instanciate multiple peristent enmaps together.

The method takes 3 arguments:

• An array of names for the enmaps to be created.

• A Provider (not instanciated), from any of the available ones.

• An options object containing any of the options needed to instanciate the provider. Do not add name to this, as it will use the names in the array instead.

Below, an example that uses destructuring:

const Enmap = require('enmap');
const Provider = require('enmap-mongo');
const { settings, tags, blacklist, langs } = 
    Enmap.multi(['settings', 'tags', 'blacklist', 'langs'],
    Provider, { url: "mongodb://localhost:27017/enmap" });