Fix run button disable. Switching to tutorial and back to samples (#1849)

[thecoder93]

Hi, This should fix the problem #1849
I think that the first time the model is created and then the get is done. For samples kataSection is undefined and I don't know why the EntryPoint is missing. What do you think? Probably it's only a workaround.

[thecoder93]

I saw that this workaround is not good, because there are same kata into different editor. I will work on it.

[thecoder93]

I understood. From Monaco doc: Each model is identified by a URI. This is why it's not possible for two models to have the same URI.

Currently, we don't have the IDs for samples. Do you think to add it? I see also missing the structured type for Sample under npm/qsharp and the relative getAll such as Katas.
I think that with this we could have the independent ids for katas and Samples, thus when we do getModel from Monaco we get properly id.

[thecoder93]

After several tests, I noticed a side effect when using updateDocument. Then the file is not closed with closeDocument. This should solve the problem. I think independent uri are therefore not necessary, or they would be an NTH.
What do you think?

@billti @minestarks