friendly error messages

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@4014 1f8fe7d8-47f0-464c-8d0a-336f4953ab05
build auto version (2998) ...

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@4015 1f8fe7d8-47f0-464c-8d0a-336f4953ab05
friendly error messages

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@4016 1f8fe7d8-47f0-464c-8d0a-336f4953ab05