E.g. 'iPad' would become 'Apple - iPad'

refs #3962 - implemented new detection of browser engines. Merged old reports from UserSettings plugin to DevicesDetection plugin. Added segment option for browser engines. Added update script to move old archives and to update old visits with engine data

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

fixes #4609

Added namespaces to functions.php files in the five plugins that had one
Work in progress

Refs #4059 Work in progress: Conversion to use Namespaces: Period*, Metrics, Segment, SegmentExpression, PluginsManager.
Removed some deprecated code.

Also moved some other const to Piwik class.

such as removing duplicate code and a lot of refactoring, the code is now much more readable!

Introducing new PluginsArchiver class. Plugins can create an Archiver inheriting this abstract class.