Move to 'qsharp' npm package and tag correctly

[billti]

We have the 'qsharp' npm package name also now. We should move from 'qsharp-lang' to it.

Also, the ADO ublishing pipeline should now tag correctly if the publishConfig settings is populated in the package.json, e.g.

"publishConfig": { "tag": "dev" }}

So our version.py script should set this to 'dev' or 'rc' as appropriate (or leave empty to default to 'latest').