Mediawiki: disable cache to be faster

[:*]
[:en]On fresh install Mediawiki v1.20.2 could be really slow. During installation process, installer proposes to enable cache just now. But when the wiki is installed it takes too long to receive a response from server. The reason is that cache system slows down performance.
[:ru] Чтобы Mediawiki v1.20.2, сразу после установки, не тормозила безбожно, просто отключите кэш. Включите, когда он реально понадобится.
[:*]Proof: [REOPENED] Caching issue makes MediaWiki painfully slow