Some typos, init with braces and explanation for semicolon at the end of struct

• Most of the modifications are typos.
• In classes, I use braces to initialize a default attribute value right after it is explained to do so (instead of =)
• I changed 2 links that were mentioning parshift, but the links were to isocpp.
• I added a paragraph to explain why we put a semicolon at the end of a struct and class (maybe because I see this error too often with ENSTA students)
• I added a note about prefixing an attribute with an underscore that is reserved to the standard
• Some code cells were in markdown

added Documentation label

changed the description

added 2 commits

• 6da32fb5 - Reformulate the paragraph about ; at end of struct.
• f478f350 - Typo.

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@vrouvrea I've just pushed two modifications and the first one needs to be validated by you.

If ok; I will merge this contribution.

I agree with your changes. I let you merge and see in which order you want to do it with #20 (closed)

Merged into master through cherry-picks (to help solve a conflict in notebook).

closed