GPU Calc: use parallel reduction to implement sum

Use reduction kernel when given a large DoubleVectorRef

Change-Id: Ifd4977b81be64274733909e43f0e5ef161bb455e

Signed-off-by: I-Jui (Ray) Sung <ray@multicorewareinc.com>
GPU Calc: implemented parallel reduction for SUMIFS

For now only works for fixed and sliding fixed-sized windows.

Change-Id: I25e3f893a86d0e1723ae1e1633ffeeee93926b8d

Signed-off-by: I-Jui (Ray) Sung <ray@multicorewareinc.com>