Unify version tag and automate release

[Jegp]

This issue tracks the unification of the version number and the automation of NIR releases.

From @sheiksadique

I am not certain how you typically deal with release management, so I can't comment about its complexity.

But there are essentially two places where the version is maintained still:

1. the **init**.py file

2. git tag/version.

It is therefore possible in principle to have these two things out of sync.

There are essentially three advantages to automate the process of releases.

1. There will be a unique location of version information.

2. The releases themselves can be automatically handled ie you do not need to create a separate release. A simple act of tagging should automate a major/minor release.

3. Any versions that are not explicitly tagged but pushed to the repos can still be published as pre-releases giving users immediate access to this without having to look up things in GitHub.