Update build tools to handle folders inside Crowdin projects

Update crowdin build tools to handle folders inside crowdin projects. A path to a parent folder should be specified to retrieve the translation files.

Take the following as an example:

all
├── de
│   ├── messages.json
│   └── nuxeo-ui-elements
│       └── messages.json
├── fr
│   ├── messages.json
│   └── nuxeo-ui-elements
│       └── messages.json
├── ja
│   ├── messages.json
│   └── nuxeo-ui-elements
│       └── messages.json
└── pt-PT
    ├── messages.json
    └── nuxeo-ui-elements
        └── messages.json

An empty parent would return the first line of message.json files whereas parent = `nuxeo-ui-elements` should return the message.json files inside the nuxeo-ui-elements folder.