Enforce consistency of pack, docs, osgi, maven tasks.

Instead of scattering properties all over invocations of
staged-docs, staged-pack, make-bundle, copy-bundle and mvn-package,
these are now all fully determined by the project they act on.

The varying arguments to these macros are all centralized.
They are named like `project.prop`, where `prop` is one of:
description, package, dir, name, namesuffix, version,
targetdir, targetjar, jar, docroot, skipPackage, srcdir, src, srcjar.

The defaults for these properties are computed using `init-project-prop`.
De-duplicate logic in maven deployment.
Render relevant properties to buildcharacter.properties
Extra repository hook via `extra.repo.url` var

Previously defaulted to 'https://oss.sonatype.org/content/repositories/releases',
now must be set manually. PR validation uses it to configure the repository
that has the artifacts published during validation.
More useful ant targets for faster pr validation
IDE needs actors/swing/continuations publish for validation.

As soon as they are also modularized, we can go back to
only building/publishing the core (lib/reflect/compiler).
Merge pull request #3108 from adriaanm/faster-build

Faster PR validation