New branch develop-ascraeus for 3.1.x

[nickvergessen]

Hi everyone,

As we released 3.1.0-b1 yesterday, we branched off a new development branch for it:
develop-ascraeus

Bug fixes should be created against develop-olympus or develop-ascraeus, depending on the fix version. New features should be created against develop. We may also merge currently open PullRequests into develop-ascraeus, so there is no need to close and recreate them.

Note for developers: Like with develop-olympus and develop before, all commits from develop-olympus should be in develop-ascraeus and all commits from develop-ascraeus should be in develop. The wiki page has been updated to reflect this.