more verbose error messages, refs #2

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@15796 29f149b2-0c63-11e1-8f5c-a347f6a9acd0
more csv2xml tests, refs #21

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@15797 29f149b2-0c63-11e1-8f5c-a347f6a9acd0