Merge pull request #6169 from piwik/3490_user_id

config/global.ini.php

core/ArchiveProcessor.php

core/Common.php

core/DataAccess/LogAggregator.php

core/DataArray.php

core/Db/Schema/Mysql.php

core/Metrics.php

core/Plugin/Report.php

core/Tracker.php

core/Tracker/Request.php

core/Tracker/Visit.php

core/Tracker/Visitor.php

core/Updates/2.7.0-b2.php

core/Version.php

js/piwik.js

lang/en.json

libs/PiwikTracker/PiwikTracker.php

piwik.js

plugins/API/API.php

plugins/API/ProcessedReport.php