D8 - More like this support

@jover, how can I test this patch? Can you provide a list of steps?

I was able to to test this patch with the following:

before the patch:

$ drush cache-rebuild && drush php
Psy Shell v0.8.11 (PHP 7.0.22 — cli) by Justin Hileman
>>> array_map(function ($x) {return $x->search_api_id;}, views_get_view_result('elastic_content', 'default', 'entity:node/2244:en'));
=> [
     "entity:node/2244:en",
   ]
>>>

after the patch:

$ drush cache-rebuild && drush php
Psy Shell v0.8.11 (PHP 7.0.22 — cli) by Justin Hileman
>>> array_map(function ($x) {return $x->search_api_id;}, views_get_view_result('elastic_content', 'default', 'entity:node/2244:en'));
=> [
     "entity:node/2248:en",
     "entity:node/103:en",
     "entity:node/1179:en",
     "entity:node/1475:en",
     "entity:node/490:en",
     "entity:node/1494:en",
     "entity:node/1466:en",
     "entity:node/1893:en",
     "entity:node/1424:en",
     "entity:node/1905:en",
   ]
>>>

Updated the location where you add the more like this query. This is now rendered beneath the original build query. Because the more like this query was overwritten by the original build query.

Also changed the query parameter of the more like this query as this needs to append to the original query when available or needs to work on its own.

Thank you for the patch. It has been applied.