Allow language files to be written as nested js objects instead of a single level

[julianlam]

A developer stumbling block relates to i18n and l8n, in that there is an expectation that:

• for a language key such as [[my-file:category.key]]
• the language file source would be found in /en-GB/my-file.json
• my-file.json would be defined thusly:

{
  "category": {
    "key": "localisation"
  }
}

Whereas in reality it is actually:

{
  "category.key": "localisation"
}

We ought to support both because the former is used by some other frameworks (laravel perhaps?)

To work with our existing system, it is likely the file itself would just be parsed and then flattened before being send to the translator (whereas right now I bet it's something even simpler, like require('that-json-file');

Maybe there's even a lodash method for this hah!

[julianlam]

Keep in mind core translations cannot be written in this manner, as Transifex expects a straight key value JSON file.