config-parent: Substitute properties in the default config file

Currently, default-config.xml is packaged as is. As version bumping scripts only edit pom.xml files, so version strings in config files are not bumped. But for INTEGRAT-37 automated bumping is necessary.

This Boron Improvement would allow maven to perform "filtering", which means it would replace (strings that look like) references to maven properties with the property values. No config files (other than the distribution one for INTEGRAT-37) currently refer to properties.

The change in config-parent is fairly small, so it could be back-ported to Beryllium easily.