[tycho-dev] master is now Tycho 4.0.0-SNAPSHOT

[Christoph Läubrich <laeubi@xxxxxxxxxxxxxx>]

Due to some incompatible changes and to account for other changes in the 
pipeline (most notable improving testing support in Tycho) I have raised 
the version to 4.0.0-SNAPSHOT now.

To track progress and get an overview it would be good if issues that 
should go into 4.0.0 before the release are tagged with the milestone, 
so if you have any breaking changes in mind please create tickets and 
assign a milestone.

I won't set a release date (yet) but I think we can aim for the end of 
the 2023-03 release for this.