This reverts commit 745c6c6d.

The ultimate prize and final step to close the issue: do not group by the whole set of matched rows, way too slow on huge datasets!

Introduce new $limit parameter to the query builder, which will LIMIT all queries including inner ones - do not use when aggregating or it will sample

This is only a start. Especially the Tracker model contains quite a bunch of different models. Ideally, one day, the tracker is refactored and all the goal tracker stuff including the queries are in the goal plugins, all the ecommerce stuff is in an ecommerce plugin etc. Haven't moved some of the LogAggregator queries.

coding style fixes, some PHPStorm inspection fixes, improved readability of code, few refactorings, all as part of our code cleanup strategy

Piwik is a free/libre analytics platform. Refs #4455 GNU Package requirement to use free/libre instead of open source

Fixes #4503 visitConvertedGoalId now works in all reports. Note that this also fixes another bug in the Ecommerce items reports!

refs #4609

Improvements in queryEcommerceItems function which make it works with segments query builder

Adding MetricsFormatter class which knows how to format/display metrics (time, money, size, etc)