Releasing 9.0.0-M1 and the other minors

[Andrea Del Bene]

Hi,

with Wicket-6563 being solved, I think it might be the right time to 
release the first milestone of Wicket 9. There are also a decent number 
of solved issues for Wicket 8. Shall we release 9 M1 along with 8.4.0 
and 7.13.0?

I also have another question: who has the right on Jira to create new 
versions (for example 9.0.0-M1)?

Thank you.