Add support for GridSample + Minor changes

• Add binding of GridSample aidge_onnx#44 (closed)
• Expose mem_manager and save_to_json
• Fix typo in attribute name for GridSample
• Explicit error during code generation:
  • Raise error stating if a template file is not found
  • Add context on which operator failed to generate a file (instead of just having Jinja error)