globa ExtraSettings.php was not being loaded

jobs/_shared/ExtraSettings.php is shared by any PHP script. Turns out
the PHP snippet was missing a slash in the path which prevented the file
from being included :(

Change-Id: If2168deba37e0a2e61bb92a63b6ee4514f9b920e
(bug 43059) $wgShowExceptionDetails = true

Globally enable full stack trace on exception. That would give some
useful details to the developers instead of the useless message: Fatal
exception of type MWException.

Change-Id: I4dd5fa2e8dd3695f2922a4cee5eb704aa1f5332f