Consolidate on one error handler.

There were a lot of suspicious calls to set_error_handler and
restore_error_handler. One of them was clobbering the
onWikiFactoryExecute call to setup the WikiaLogger::onError handler.

/cc @nmonterroso @owend
Remove the AFPRegexErrorHandler.

The error handler was pushing the exception throwing into the
set_error_handler callback which I don't think is a good idea. The
exception will be thrown anyway and the error will now be forwarded to
ES.
Remove setErrorHandler. It's not being called.
Remove the error handler from WebStoreCommon.
Merge pull request #3769 from Wikia/one-error-handler-to-rule-them-all

Consolidate on one error handler