ant: release target archives release version metadata

tools/source-archive creates and repacks the source release,
and embeds ant and cmake version metadata in the release.
ant/version.xml conditionally includes ant/gitversion.xml,
overriding the use of git when building from a source
release.  This file will never be present in a source
repository.
cpp: cmake uses embedded version metadata
ant: release target works when run in a submodule

Check for presence of .git, not whether it's a directory.
Update top-level pom.xml to allow building from source packages
ant: version and shortversion are the same
Merge pull request #894 from rleigh-dundee/zip-build50

Make a buildable source release (5.0)