Support for Solr 6.x and 7.x

[vengador]

Some of the Solr modules in drupal (https://www.drupal.org/project/search_api_solr/releases/8.x-3.9) are not supporting Solr 4.x. I have tried to make Solr machine works with this version but looks like Solr Package structure is a little bit different. We would need to review what is failing when we change Solr version and it makes our version doesn't work.