Adds comment hinting at how to put a display name in web.xml.erb file.

One line comment about display name for Tomcat Dashboard. Brainstormed ways of auto-generating this name but not successfull, better to just add a comment to hint to power users that it can be added to a web.xml.erb template. 

Thought about using Rails.application.class.parent but since that assumes a Rails env that would be bad. Plus if display-name appears in the web.xml it will likely be used over the filename by Tomcat. Settled on just adding a comment file to the file so that power users knows it exist and don't have to dig Tomcat config files like I had to.