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

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

using phpstorm optimize imports feature

UserAgentParserEnhanced is now required and used from it's own composer package (piwik/device-detector); additionally Spyc library is required as composer package and removed from piwik source

fixes #4609

improved methods to get browser/os logos. always try to find an accurate logo, use family logo if no specific logo is found. never return unexisting path, return transparent logo instead

Errors in Scheduled Reports cron: make sure image files are valid (new test checks PNG files are really PNG, etc.)

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

 * making tests pass!
 * enabling DevicesDetection tests, even though DevicesDetection plugin is disabled by default.

 * making some tests pass == fixing bugs

Adding new DevicesDetection plugin, developed by Clearcode and sponsored by a client of Piwik Professional Services. A beautiful work of engineering, all released under GNU/GPL license!

Fixes #3612
 * when enabled, the plugin will add a new submenu: Visitors> Devices
 * the new devices report contains NEW reports:
  * Much improved Device type (tracking 'car browser', 'console', 'desktop', 'feature phone', 'smartphone', 'tablet', 'tv')
  * Device brand (tracking more than 100 brands such as Nokia, Nintendo, Lenovo or Apple.
  * Device model (tracking hundreds of phone/console models)
  * Operating System versions (tracking 70 variations of operating systems including Ubuntu vs Kubuntu vs Debian vs Lubuntu vs Xubuntu)
  * Operating System families (Android vs Google TV vs Windows vs Windows mobile vs Mobile gaming consoles)
  * Browser versions
  * Browser families

Refs #3505 There is some basic TV detection included and maybe you can help contribute better detections (see the .yml data files containing the regular expressions in YAML format)

HOW DOES IT WORK

This is quite beautiful system. It is a plugin that disabled by default. when enabled, it will create additional columns in the DB. Also at tracking, it will look at the user agent, and try to match it against one browser we know in the databases. The databases of user agent matching are composed by 3 YML files, parsed by spyc.php into php array.

These 3 YML took dozens of hours of work and testing with dozens of mobile phones and devices for accuracy. We are happy with the result as they should cover > 80% of the devices commonly used. We hope the community will help us build up these YML files and make them better, so we can track accurately 90% or 95% of requests.

The performance overhead is pretty small, but parsing the YML files + running dozens of regex will add some overhead. This is why it is still disabled by default. We will think about how to integrate it in core, in the next few months.

Please let me know if you find any problem with this new awesome code!