Revert "Consolidate parts of WebStart.php and doMaintenance.php into Initialize.php"

Good idea, but moves things about too much and will break things. Let's revisit and not break things.

This reverts commit 214931ed33124a36e01e105c41c7d7e4797bde82.

Change-Id: I6f5026b572105cd9e7d6de12a491c7ee45ac3dbc
(cherry picked from commit 280d7a92fdb214d814b890b580a6166844547b46)
Merge "Revert "Consolidate parts of WebStart.php and doMaintenance.php into Initialize.php"" into wmf/1.24wmf19