Test enhancement

[peter279k]

Changed log

• Since the PHP package requires php-7.1 version, it should upgrade PHPUnit to ~7 version semver.
• Using the PSR-4 autoloading for InterNations\\Component\\Solr\\ and InterNations\\Component\\Solr\\Tests\\.
• Removing some attributes on phpunit.xml.dist file because they're unused and invalid.

The PHPUnit warning messages are as follows:

  Warning - The configuration file did not pass validation!
  The following problems have been detected:

  Line 10:
  - Element 'phpunit', attribute 'strict': The attribute 'strict' is not allowed.

  Line 21:
  - Element 'log', attribute 'title': The attribute 'title' is not allowed.
  - Element 'log', attribute 'charset': The attribute 'charset' is not allowed.
  - Element 'log', attribute 'yui': The attribute 'yui' is not allowed.
  - Element 'log', attribute 'highlight': The attribute 'highlight' is not allowed.

  Line 23:
  - Element 'log', attribute 'logIncompleteSkipped': The attribute 'logIncompleteSkipped' is not allowed.

  Line 27:
  - Element 'blacklist': This element is not expected. Expected is ( whitelist ).