Provide API to get all the JNLP artifacts

This is a request from Java SE Advanced team. We're implementing a tool that will allow Java administrators collect statistics about Java applications (with Java Usage Tracker) and create deployment ruleset based on the collected data.

Java Usage Tracker reports very basic information only. For example, for JNLP applets and Web Start applications it reports JNLP file URL only (sometimes, even this URL is not accessible). However, deployment rules can be created based on other fields, e.g. certificate used to sign jars.

So one of the parts of the tool is for any given URL of a JNLP file get all the artifacts (jars, extensions, etc.) We have basic implementation for this, but it may or may not be exactly the same as what is used by Java Plugin and Web Start. It would be fine if the Deployment team can provide public/internal API for this purpose instead.

There is an alternative approach, though. We can use our own implementation to parse JNLP files. In this case we'll need support from SQE to test if our implementation match the Deployment code, and if it doesn't we'll have to find out if it's a bug in the tool or in JRE.