Currently we use internal arg ids for specifying bundleArguments.
For example,
        <fx:bundleArgument arg="mainJar" value="hello.world.jar"/>
        <fx:bundleArgument arg="win.exe.systemWide" value="true"/>
        <fx:bundleArgument arg="signBundle" value="true"/>

We shouldn't allow users to use internal argument ids. Instead, they will need to use new arguments ids (without "--"), like this:
        <packager:bundleArgument arg="main-jar" value="hello.world.jar"/>
        <packager:bundleArgument arg="system-wide" value="true"/>
        <packager:bundleArgument arg="sign" value="true"/>

In case the value specified for "arg" is not new arg id, we need to show a warning and ignore it.