Adds support for multi-release jars (for JDK 9+); fixes a few bugs with Spring-Boot jarfile scanning.
Multi-release jars: If a path META-INF/versions/X exists in a jarfile on the classpath, where X is an integer greater than or equal to 9, and less than or equal to the running JVM version, then this path is used as the scanning (and classloading) root for the jarfile. If there are multiple multi-release package roots, the highest number less than or equal to the running JVM version is used.