Add version number to a parameter set

[valentinsulzer]

Add version number to a parameter set, separate from (in addition to) the BPX version number.

This would allow us to fix mistakes or inaccuracies in parameter sets while maintaining old versions (and hence not changing any previous results/publications that have been obtained using an old version).

It can probably just be a single version number, doesn't need to be semantic versioning.

[rtimms]

Add a new field to the Header, e.g.

    version: str = Field(
        None,
        alias="Version",
        example="0.1.1",
        description="BPX file version",
    )

@Ubham16

[rtimms]

Fixed by #63