Timeline v6.0.0-rc.1 (Patreon)

I think it's good to go now. Let's wait a few days, see if another issue appears and then I'll release!

NOTE: The build was deleted because of an issue resulting in loss of triggers

- Stop and Reset should always sample the keyframe and apply the pose
- Fix tracks copy/paste issues (loading crashes, naming conflicts across segments and layers, missing validation)