Only Python code generation is possible

Right now, it's only possible to get and show the python translation of the blocks.
This is hardcoded here : https://github.com/UCL-INGI/INGInious-problems-blockly/blob/2e52641c8ca8a95c1c93d704308645dc18aeeb8b/inginious-problems-blockly/static/blockly/blockly.js#L224

There should be an option in the task editor that allows to change that. For example, if one wants to get back the javascript equivalent.

Start at static/blockly/blockly.js around line 224, where Python translation is hardcoded, and trace how the task editor supplies configuration. Add an editor option for the available code-generation language, including JavaScript, and verify that the selected translation is returned and shown instead of always using Python.

索引モデルが issue の本文から書いたものです。