Added manual pages for 3 warnings, fixed typos in other warning pages

git-svn-id: http://umple.googlecode.com/svn/trunk@3200 6ebf9d09-8eb1-0036-9d08-68c07d1b990a
added warning pages to en.error

git-svn-id: http://umple.googlecode.com/svn/trunk@3201 6ebf9d09-8eb1-0036-9d08-68c07d1b990a