Improve error reporting

[r0ller]

Check if the syntax error reporting function (https://www.gnu.org/software/bison/manual/html_node/Syntax-Error-Reporting-Function.html) can be used for structured error reporting.

Semantic error reporting (missing mandatory dependencies especially) needs to be developed as well.

These two would pave the way for a basic use of natural language generation algorithm so clients don't have to hard code error messages but could call an nlg api function to generate it based on the structured error report passed to it.