integrating some developments from COLOMBO: PHEMlight, E2 TraCI support extensions, small code improvements

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@15707 29f149b2-0c63-11e1-8f5c-a347f6a9acd0
adapting duarouter to new empty flow behavior, refs #1157, #21

git-svn-id: http://svn.code.sf.net/p/sumo/code/trunk/sumo@15708 29f149b2-0c63-11e1-8f5c-a347f6a9acd0