Suport Alfresco version 4.2.x
Currently it only checks to see if the user is admin.
The plan is to have a group that can be changed by editing siteCreateGroup.
Auto deploy is set to true.
Create a jar file
jar cf ../RestrictCreateButton.jar
Then deploy the file to shared/lib or to webapps/share/WEB-INF/lib folder. Restart tomcat.
References: http://stackoverflow.com/questions/22531555/how-to-hide-create-site-link-for-particular-user