Adding Product file for prepare release.

[MohananRahul]

Product files also need to be updated.

[akurtakov]

Is tycho-versions-plugin updating product files when run locally?

[laeubi]

If we include products then actually also features should be included, but also here we should check that they actually gets a version change (as the version needs to match the release) but the title is a bit misleading as it talks about prepare release (that only updates the parent), but you actually change the update release workflow.