Fix for version file for launcher + increment to next major release

[Cervator]

This quick-fixes Terasology/Index#16 and should let the launcher identify newer Omega zips from Jenkins, as the versionInfo.properties is again attached from a slightly updated path then retrieved during the Omega zip making.

Goes with Terasology/Index#17

Additionally I think we're overdue for bumping the engine version to the next major, considering the next release will include the major upgrade to Gestalt v7, that definitely deserves a bump.

If no objections we should also adjust the current milestone accordingly: https://github.com/MovingBlocks/Terasology/milestones/45/edit

And I think #4509 should probably be closed as complete as part of that? I know there are still leftovers floating around, but that core issue seems to deserve its finished status 👍

Omega fix confirmed with https://jenkins.terasology.io/teraorg/job/Nanoware/job/Omega/job/develop/34/

[Cervator]

Omega builds have no versionInfo

[keturn]

Limit PR scope to a single issue, please! Unless the issues are intertwined, but that doesn't look to be the case here.

I'm picking on this one a bit because while it is often quite practical to include some one-line change along with the other work in a PR as some bit of incidental cleanup, this PR description talks more about the things that aren't the targeted issue than the fix itself.

(despite me picking on it, I recognize there is more description of the issue and its fix on both Index#16 and Index#17)

I do agree that this change to the Jenkinsfile in combination with the linked change to Index/Jenkinsfile should be sufficient to repair things.