Add new JarUtils class

This release adds a new JarUtils class that provides methods related to Java JAR files:

• getClasspath assemble a classpath string from the specified array of dependencies.
• findJarPathFor find the path to the JAR file from which the named class was loaded.
• getJarPremainClass gets the Premain-Class attribute from the indicated JAR file.

These methods are especially useful for building command lines to spawn Java processes.