Fix error in edits_web table

We can't use null in UNION because the newly added column is not the
last column.

Bug: 56979
Change-Id: I022312e2bd464585d823e965132b72063ec044f3
Remove performance graph

Generating it is very costly the way it was done and we'll be moving to
use ganglia/graphite instead for performance monitoring.

Change-Id: Ia7d9f5850a2279449c4bda043c5df7b7b5328409