REVIEW: DefaultRankingFunction.maxRank should take account of potential @Priority values

Where DefaultRankingFunction doesn't take account of potential @Priority values when calculating the maximum potential rank contained in a given Injector. See linked issue for more details if interested.

https://bugs.eclipse.org/bugs/show_bug.cgi?id=441912
http://bamboo.s/browse/NX-OSSF210-1 :white_check_mark: