Included $resolution for generating the Config Hash of the Visitor #109

The $resolution on the function getConfigHash seem to have been ignored for generating the visitors configuation settings hash. Added that to the md5 function.

I'm not sure if it's that good to add it to the hash. Resolution might change within one visit, maybe just by moving the browser window to another screen (with different resolution)

I think it was there at one point and then removed... does resolution change when orientation changes?

resolution changes within a visit, so we cant use it to seed the hash...

In that case we should at least remove the parameter from the function.

good point, done in https://github.com/piwik/piwik/commit/a0d277eda478650082d27406a60cc927beddeb34