Allow to bypass version check

[adrienball]

Description:
This PR adds the ability to bypass the model version check which is performed when loading an nlu engine with the from_path API:

from snips_nlu import SnipsNLUEngine

engine = SnipsNLUEngine.from_path("path/to/nlu_engine", bypass_version_check=True)

The version check is there to ensure compatibility between the loader (the library itself) and the loaded (the trained engine directory/bytes). If the two versions don't match, then an error is raised and the loading is stopped.
The actual incompatibility often depends on the NLU configuration used, which is why it can be useful to disable this check for cases where the trained data is known to be compatible with the new version of the library. In such cases, a warning log will be emitted.

Checklist:

• My PR is ready for code review
• I have added some tests, if applicable, and run the whole test suite, including linting tests
• I have updated the documentation, if applicable