cherry pick fix rev 3481 (esssion storage fixes)
plainbox: increment version to 0.17.1.dev
plainbox: increment version to 0.17.1
plainbox: increment version to 0.18.dev
"Release_2014_Week50 [r=sylvain-pineau][bug=1331302,1341769,1347120,1382321,1383447,1387782,1387843,1388055,1388747,1389253,1399481][author=checkbox-dev]"