Configure a mechanism for versions to stay in sync

[andreiborodin]

Today we have 3 places where we gotta keep versions in sync:

• This common props file
• package.json for the UPM package
• The NuGet build project

We need to figure out a method for keeping them in sync.

[andreiborodin]

Also, we should update NuGet versions to also be incremented. This doesn't only mean for packaging, but also for consumption.

[andreiborodin]

The change above didn't cover:

• Mechanism for updating the templates used in generation that are part of MSBuildForUnity NPM package
• Mechanism for keeping the NPM package.json version in sync