Brought more consistency to the grammar and made important things optional.

- forced closing tags to match the latest opening tag, considering the id
- made it possible to parse alone unmatching closing tags, considered as "orphans"
- made the id of opening tags optional
- removed some useless remaining stuff
Now it is possible to know when the parser failed.

- fixed the update method of code, and now actually returns the update result to the client
- now an alert is displayed when the parser couldn't parse the source, until it can finally do it again
- enhanced code and documentation of the alert method, and made possible to disable the close button
Brought validation out to the user.

- the mode can now return data about validation, basically a list of errors
- the web app can display those errors, validation is requested in live edition