#6635 rename phpunit.xml to phpunit.xml.dist. did not know it is supported out of the box by phpunit

- renamed code coverage tests units to new structure
- removed processed system test files from git, added to .gitignore

refs #5940 put tests in correct folders, better testsuite names, some tests still fail and I cannot figure out why

refs #4996 maybe this fixes the not working tests on travis? maybe the sqlite version returns the result in a different order

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

- Make 'idsite' parameter in certain Overlay URLs 'idSite'.
- Make sure Overlay sidebar has width so screenshot test framework can find position.
- Add overlay test site so Overlay can be loaded in phantomjs.
- Remove createSuperUser call from TrackerTest (done in Fixture setUp).
- Make sure piwik.js link is created for screenshot tests & make sure the test environment JSON file is loaded after the database is setup.
- Modify logic that waits for images to load in screenshot testing framework's page renderer to wait for CSS image URLs.

Fixes #4614 Remove VisualPHPUnit from the codebase, since we don't use the tool anymore (everyone using PHPUnit in command line)

PHP Tracker and Tests fixtures
Schema updates

Refs #4087, add UI screenshot tests to new repository, enable tests on travis and make sure new repo is built every time integration tests pass on piwik build.

Remove composer.lock from .gitignore

Refs #4019

[ci skip]