BUG: Remove multiple per-pixel allocations in Mahalanobis Membership

When using the VectorConfidenceConnected filter multiple per-pixel
dynamic memory allocations were being performed. This patch removes
that by manually doing the vector matrix vector operation, with out
creating any temporaries. It was observed that this gave a 1.8x speed
up when segmenting the blue ice in the Visible Human.

Change-Id: I54c4a40604bd10d32ec4c401c3f195d436028045
Merge topic 'RemoveMemoryAllocationMahalanobisDistMem'

c5346503 BUG: Remove multiple per-pixel allocations in Mahalanobis Membership