fixing typo in mean speed calculation, refs #254

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@16614 29f149b2-0c63-11e1-8f5c-a347f6a9acd0
adapting detector outputs to new interval, refs #1171, #254, #21

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@16615 29f149b2-0c63-11e1-8f5c-a347f6a9acd0