Create a satellite site for NEV 2.x

Since the release of the 2.0.0 version of the NEV stack, NEV has become independent of the Nuxeo Platform. It has its own versioning, and it is now compatible with Nuxeo LTS 2019 and 2021.

Thus we need to document it independently from the Platform, for that we can use the same mechanism as Client SDKs, the satellite sites.

Furthermore, as this new release came with some changes, like the artifact names for instance, the whole NEV documentation should be reviewed.