Filter parameters user-changeable from Admin Center

Do not expose for modification values that should not be changed by user/admin.

That's especially true for "system" and "jdk" values. Some should be displayed as read-only, and others should even not be displayed.
I think Product Name and Version should stay changeable as the user may want to display his product name and version instead of Nuxeo generic values.
Of course, that must be different properties than internal values about the running Nuxeo product name and version.