Minor changes in the "Optian sources" section
Corrected faulty link syntax
Moved some parts to the wiki
Removed warnings
Corrected faulty namespace for autoloading
Corrected return value in doc block
fixed typos, added more keywords
Fixed: missing namespace location for type hint
Fixed: added missing arguments for variable_set() function.
Merge remote-tracking branch 'origin/master' into drupal-testing