list type values are not additives in glide config

[kdabir]

If glide app provides a list value, values set by template app are lost. An example is listener. If app needs to have it's listener included in the list, currently one has to provide the listener added by glide as well otherwise on listener provided by the app remains in the merged config.

listeners = ['groovyx.gaelyk.GaelykServletContextListener','myapp.MyAppListener']