wikichecks - additional check & cleaned-up

* added param '' where lang key 'gwtoolset-permission-not-given' is used without a param
* added checkMediaWikiVersion()
  - used wfUseMW instead of using version_compare() directly
* added Config::$required_mediawiki_version for use with checkMediaWikiVersion()
  - set requireved version to 1.22c
* moved self::checkMediaUploadSettings() to the bottom of pageIsReadyForThisUser()
* removed @return {void} comments
* renamed verifyPHPVersion to checkPHPVersion

Change-Id: Ia5a7661c5c0b6854e9ed5e9dd2e14b4bb9f25f8b