timeShift Function doesn't graph all data when used inside sum() with wildcards

[Nicholas Leskiw]

if using wildcards and timeShift() inside a sum()

for example:
sum(timeShift(graphite.servers.*.errors.java.*.count,"7d"))

two problems occur:
1. Only the first match to the wildcard is summed to itself (so if there's 42 metrics, you'll get a graph of the first metric with a scale of 42).
2. As more metrics match, the function takes exponentially more time to complete.

With 42 metrics, it takes nearly a minute to draw the graph (incorrectly).

A quick fix is to use timeShift() outside the sum(). Either this needs to be fixed so it works properly or an error should be thrown preventing a huge CPU drain and incorrect graphs being drawn.