Try to work around double stringify.

[Carreau]

This is a weird issues due to combinaison of upgrades that will be tricky to work around.

for some reason gulp-typescript do not warn of not-matching types, and a String end up being used as an object, leading to double serialisation, and late faillure at deserialisation.

so now to work around you have (sometime) to work around the doubled serialized notebook by JSON.parse twice. Which is a bit brittle, I think but should work.

[Carreau]

• [x] creating new .ipynb
• [x] creating subfolder
• [x] creating .ipynb in subfolder
• [x] pure text file seem to work also.

Merging for now to test more.