Adds optional $config parameter to API instance constructor

[vedmaka]

The change adds optional $config parameter to MediaWiki instance constructor. With the optional $config param it's not possible to supply internal Guzzle client with extra parameters [1] like timeout and connect_timeout.

Additionally there is a special noretry flag added to be processed by MiddlewareFactory to allow to disable 5x retries which are enabled by default.

For example:

$api = MediaWiki::newFromEndpoint( 'https://mywiki.com', null, [
    'timeout' => 60,
    'connect_timeout' => 30,
    'noretry' => true
] );