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`.