8u40 API Review: RT-37767 Provide friendly APIs to access User JVM Preferences

[Danno Ferrin]

webrev: http://cr.openjdk.java.net/~shemnon/RT-37767/webrev.0/
Jira: https://javafx-jira.kenai.com/browse/RT-37767

This is the proposed API to allow the friendly access tot eh User JVM Options.

Here are some snippets from demo code on my machine showing how they may 
interact:

        // get the helper instance
        UserJvmOptions ujo = UserJvmOptions.getUserJVMDefaults();
        Map<String, String> userOptions = ujo.getUserJVMOptions();

        // print out all the options currently set
        for (Map.Entry <String, String> entry : userOptions.entrySet()) {
            System.out.println("key:" + entry.getKey() + " value:" + 
entry.getValue());
        }

        // if we haven't marked the first run, do so now
        if (!userOptions.containsKey("-DfirstRunMs")) {
            userOptions.put("-DfirstRunMs", 
Long.toString(System.currentTimeMillis()));
        }

        // add the last run
        userOptions.put("-DlastRunMs", 
Long.toString(System.currentTimeMillis()));

        // save the changes
        ujo.setUserJVMOptions(userOptions);

----

        // create a table row with Key, Current Value, and Default Value
        DefaultTableModel model = new DefaultTableModel();
        model.addColumn("Key");
        model.addColumn("Effective");
        model.addColumn("Default");

        Map<String, String> defaults = ujo.getUserJVMOptionDefaults();
        for (Map.Entry <String, String> entry : userOptions.entrySet()) {
            // get the default, it may be null
            String def = defaults.get(entry.getKey());

            model.addRow(new Object[] {entry.getKey(), entry.getValue(), def == 
null ? "<no default>" : def});
        }