Modernize and clean up the build.
Modernize and clean up the build.

Settings `in Global` are moved to Build.settings. Otherwise they
are added *twice* in every project.

Project definitions use the `project` macro rather than the
`Project()` factory, as is the customary notation since sbt
0.13. The `Defaults.coreDefaultSettings` is therefore dropped.

The coding style of project definitions is adapted to the style
shown in sbt documentations.

dotty-staging/dotty,densh/dotty,som-snytt/dotty,som-snytt/dotty,som-snytt/dotty,som-snytt/dotty,lampepfl/dotty,sjrd/dotty,lampepfl/dotty,sjrd/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,densh/dotty,lampepfl/dotty,dotty-staging/dotty,sjrd/dotty,sjrd/dotty,dotty-staging/dotty,sjrd/dotty