Include more useful information in saved model files

[WenjieDu]

1. Feature description

More useful and important info should be included and saved into model files, e.g. PyPOTS version, model hyperparameters, etc.

2. Motivation

For example,

the saved PyPOTS version can be utilized to check for compatibility; saved hyperparameters can make PyPOTS directly load from the saved file;

3. Your contribution

Will make a PR in the future.