Enforce https one marketplace.eclipse.org

In an effort to protect the Eclipse Marketplace users, we will enforce HTTPS for all solutions in a 4 steps process:

• On September 20th; we will display a banner on the marketplace website to start notifying people about this process. No change and no breakage at this point. Mikael will publish a blog post at the same time to elaborate on the reasoning and value.
• On October 14th October 20th; validation rules will be added to the marketplace website: solutions cannot be added or edited with plain http links; only https will be accepted.
• On December 15th, we will un-publish all solutions having plain http links. We will reach out to owners one last about the unpublishing of their solutions, giving them 45 days (until January 30th) to fix them. After this date, solutions that don't match the new requirements will be permanently removed.
• On January 30th, we delete all non compliances solutions.

Here is the communication plan with plain HTTP solutions owners:

• Oct 4: first announcement to solutions owners, asking them to update their listings.
• Oct 14 Oct 20: reminder + notification of the new validation rule
• Nov 15: reminder about unpublishing in 1 month
• Dec 5: reminder about unpublishing in 10 days
• Dec 15: notification about unpublishing + reminder about deletion EOF January
• Jan 17: last reminder about deletion in 2 weeks
• Jan 31: notification about deletion