Improve settings.xml parser

Adding new properties to Advanced tab of JCP (settings.xml) sometimes results in strange bugs appear.
For example using the following fragment in settings.xml results in ClassCastException on Windows platform in com.sun.deploy.panel.XMLDocumentHandler but works fine on Mac
        
        <platform text="mac os x">
            <label text="deployment.misc.label">
                <checkbox propertyName="deployment.system.tray.icon" checked="true" />
                <permission text="admin" ifLessThanJDK8="true">
                    <checkbox propertyName="java.quick.starter" checked="false" />
                </permission>
                <checkbox propertyName="install.disable.sponsor.offers" checked="false"/>
            </label>
        </platform>

while the following one (the checbox "install.disable.sponsor.offers" just moved up) - works fine on Windows as well.
        <platform text="mac os x">
            <label text="deployment.misc.label">
                <checkbox propertyName="deployment.system.tray.icon" checked="true" />
                 <checkbox propertyName="install.disable.sponsor.offers" checked="false"/>
                <permission text="admin" ifLessThanJDK8="true">
                    <checkbox propertyName="java.quick.starter" checked="false" />
                </permission>
            </label>
        </platform>