user-dev-guide: properly fail the build when the sequence diagrams cannot be build

git-svn-id: https://scalaris.googlecode.com/svn/trunk@7007 71766da9-9752-0410-ab17-bfafa751c56a
user-dev-guide: create a main.pdf including the rrepair sequence diagrams

git-svn-id: https://scalaris.googlecode.com/svn/trunk@7008 71766da9-9752-0410-ab17-bfafa751c56a