Improve generate_question to recognize question type from YAML input file

Refactor the generate_question, so that it recognize the question type from the YAML input file. This will remove the subparsers from main (cli subcommands), modifying the entire interaction with the tool.

• Change Tests to omit subcommands
• Create a Factory for Questions
• Decouple the creation from the subcommands, remove subcommands
• Update Documentation
• Consolidate tests in one the general parsing and std.out and std.err matching. Let the question type specific tests for corner cases.