Copying code from acquia_search's PreferredSearchCoreService class into SAPIPreferredSearchCoreService

Issue #2597740 by janusman, Nick_vh: To ease debugging, add $_ENV['HTTP_X_REQUEST_ID'] (if present) to outgoing acquia_search URLs

Issue #2631240 by janusman, magtak: Module should set search_api_solr_http_get_max_length to a compatible value

Issue #2113415 by Nick_vh: Fixed Derived key is not succesfully overridden and port settings should be hidden.

Chris Johnson authored Oct 08, 2013 and Nick Veenhof committed Oct 08, 2013

Issue #2087141 by tekante: Fixed acquia_search_host() takes precedence over ['heartbeat_data()']['search_service_colony()'].

Issue #1977510 by drunken monkey, Nick_vh | rikvd: Fixed Acquia Search for Search API is incompatible with Search API Solr search 7.x-1.0-rc4.

Issue #1852692 by Marty2081, cpliakas: Fixed overridden connection parameters still used after unchecking "Modify Acquia Search Connection Parameters"

Issue #1689778 by alanmackenzie, cpliakas, Nick_vh: Added support for connecting to more than one subscription.

Issue #1619770 by cpliakas: Added default fl param as a backwards compatible change to the missing defaults in Acquia Search's solrconfig.xml file.