* Improvement to ChronologyProtector: only record the master position if a write query was done. This should help to avoid the worst of the ChronologyProtector side-effects, such as having action=raw CSS requests block for a time equivalent to the slave lag on every page view, while maintaining the benefits, like preventing a 404 from being displayed after page creation.
* Fix broken recursion guard in LoadBalancer::reportConnectionError(), which was causing getConnection() to return false on the second and subsequent errors, instead of throwing an exception. Revert incorrect fix r41229/r41230.
* We used to have parameters to ignore errors, but they're obsolete now that we have exceptions. Implemented ES master failover using exceptions instead.
* Changing the number of DB connection attempts from 3 to 2 for some random getConnection() calls is almost pointless, adds lots of ugly formal parameters all of the place, and misses the big picture. It should be 2 by default, based on the original rationale. Any reasonable implementation of failover should have zero timeouts per request, by storing state. Changed the default to 2, or 1 if a long timeout is set.
* On read, spend less time checking on dead slaves
* Add randomInsert() to ES. This does the cluster picking for us
* Make revision text use randomInsert(). On write, fails-over to other clusters as needed instead of throwing db errors
* Use an associative array to initialise LoadBalancer objects
* By default, use Preprocessor_DOM if available, otherwise use Preprocessor_Hash. Preprocessor_Hash has worse performance.
* Fix parserTests.php for replicated databases. Use CREATE TABLE instead of CREATE TEMPORARY TABLE if there is more than one server configured.
* Log exceptions even in command-line mode.
* Wrote a tool to check the integrity of the autoloader class list, fixed some issues that came up.
* Start the autoloader before LocalSettings.php, so that when an extension writer thinks an inefficient one-file special page extension is the way to go, they don't have to use explicit includes to make the class inheritance work. Should continue to work with $IP set in LocalSettings.php as long as $IP is set before extensions are included.
