Make the translation download cache bustable

Adding a config key for busting the translation cache.

__Usage:__
Change the `cacheVersion` value to anything else will force phreepio to download new translations 

__phreepio.json__
```
{
  "translator": {
    ...
    "config": {
      "cacheVersion": "v1.0"
    }
    ...
  }
}
```