File management + doc

[LeCalicot]

A few minor changes which do no affect the code in any way that I had on a branch for a while:

• splitting the json_parser in two files as the tests are very long
• rename it to parser. Ink always serialize to json
• added the doc with the ink syntax for runtime
• updated the .gitignore

[LeCalicot]

I have made changes according to the comments.