PLATFORM-142 - Database: log server IP, cluster name and DB name

@Wikia/platform-team 

More logging for https://github.com/Wikia/cheetah/pull/25

An example:

```php
Array
(
    [@timestamp] => 2014-09-16T08:55:02.317822+00:00
    [@message] => SQL SELECT /* DataMartService:getSumPageviewsMonthly  */ SUM( pageviews ) AS cnt, time_id
	 FROM rollup_wiki_pageviews
	 WHERE period_id = '3'
	 AND time_id = '12354566789121111232112112'
    [@fields] => Array
        (
            [db_name] => plpoznan
            [city_id] => 5915
            [request_id] => mw5417fae0aa6410.92866046
        )

    [@context] => Array
        (
            [method] => DataMartService:getSumPageviewsMonthly
            [elapsed] => 0.0015420913696289
            [cluster] => c1
            [server] => 10.xx.xx.xx
            [server_role] => master
            [db_name] => statsdb_mart
        )
)
```