Included note about running grails clean and grails upgrade

git-svn-id: https://svn.codehaus.org/grails/trunk@4129 1cfb16fd-6d17-0410-8ff1-b7e8e1e2867d

Author: marcpalmer

README

@@ -63,7 +63,12 @@ For more info checkout the Grails homepage at http://grails.org
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-To upgrade your existing Grails projects you must run "grails upgrade" for each project.
+To upgrade your existing Grails projects you must run:
+
+grails clean
+grails upgrade
+
+...for each project.
 
 There are some unavoidable issues that may affect you when upgrading to 0.5 from a previous version: