[eclipse-pmc] Update Release Rules

["Daniel Megert" <daniel_megert@xxxxxxxxxx>]

Hi PMC

As discussed, here's the draft note
I plan to send out regarding our rules for Update Releases. Please approve
or provide corrections.

For the Eclipse top-level project the
main goal for Update releases is still to increase stability. Therefore,
like for API changes (including additions), any feature work needs to be
brought forward to the PMC for approval. Only fixes and features that are
already working fine in master for some time can be brought forward. Having
the work first in master and tested by the community before it gets backported,
is our normal workflow. Also, any backport needs a review from another
committer.

Dani