Use JSON instead of multidimensional array in AddIPMMappedNamespaces

[isc-shuliu]

This seems like a good use of a JSON object instead of a subscripted array. Seems overly complex and harder to follow the logic with the subscripted array.
My general rule of thumb is to use a subscripted array mostly when I need de-duplication so like a set.
For a dynamic object, can look like the following (also document why ns and width are needed):

{
  ns: "*",
  width: 4,
  namespaces: {
    "USER": [
       "zpm": { "version": "0.9.0-SNAPSHOT", description: "Package Management System", devMode: 1 },
       "zpm-registy": { "version": "1.3.2", description: "ZPM Registry", devMode: 0 }
    ]
  }

Originally posted by @isc-kiyer in #485 (comment)