Add NeMo version to all new .nemo files
Signed-off-by: smajumdar <titu1994@gmail.com>

# What does this PR do ?

Adds current nemo version to all nemo files generated. 

# Note

The version will point to the *earliest* known version of NeMo that was compatible with this model. This does not preclude later versions being compatible/incompatible with the checkpoint, so it is up to the user to determine which version would work best, but it can be assumed that no version prior to the noted version will support the checkpoint.

**Collection**: [Core]

**PR Type**:
- [x] New Feature
- [ ] Bugfix
- [ ] Documentation
