Better architect releases in rule engine

[azuline]

The rule engine operates on tracks, but some metadata properties belong to releases. How can we unify releases and tracks?

Protocol: Some matchers only match entire releases; other matchers only match entire tracks. Running a release action on a track modifies its entire release.

This is almost what happens right now, except when we modify a release variable on single track, it only updates the entire release if it is the first track.

The rules engine could be rearchitected to take into account this distinction as well.