Less magic in voxel-plugins require() plugin loading

[deathcap]

The use of require() to find plugins is slightly confusing, that is, the caller passes in their own "require" function that locates the plugins, which they themselves manually require but do not assign the return value, to get picked up by browserify's static analysis. Example:

require 'voxel-artpacks'
require 'voxel-wireframe'
require 'voxel-chunkborder'
require 'voxel-outline'
… a bunch of plugins …

  createEngine {require:require, exposeGlobal:true, pluginOpts:
… plugin configuration (also required) …
    'voxel-artpacks': {}
    'voxel-wireframe': {}
    'voxel-chunkborder': {}
    'voxel-outline': {}

it may be more intuitive and less unnecessarily automagical although somewhat more verbose if the caller directly passed in the return value of require() for each plugin. Something like:

'voxel-wireframe': {
  load: require('voxel-wireframe'),
  … other options…
},

'voxel-chunkborder': {
  load: require('voxel-chunkborder'),
  …
 },

or pass in a list of where to find each plugin, and the options still separately:

plugins: [
 require('voxel-wireframe'),
 require('voxel-chunkborder'),
]
pluginOpts: {
 'voxel-wireframe': {},
 'voxel-chunkborder'; {},
}

Object literals in JavaScript use string keys so we probably cannot do something along the lines of this: (at least not in ES5?)

pluginOpts: {
  require('voxel-wireframe'): {},
  require('voxel-chunkborder'): {},
}

plus then there's the problem of finding the canonical plugin name (string passed to require()).