New branch for upcoming density work. Will add ANN as a dependency.
- Added ANN library to be used in nearest neighbor searching needed for density "function" creation.
Added some sample density data and functions to import it.

Makefile:
- copied changes from bp branch

SaveDDPoints/SaveDDVals
- sample dataset, hopefully not too large for testing

scvt-mpi.cpp
- added readDDPoints(), readDDVals() and arrays for them to read into
- added calls to above functions in main(), on master processor
Added usage of ANN to code. Reads in ddpoints into an ANN points array, then creates a kd-tree from them. Creates a set of GS points, and uses those as query points to the kd-tree, listing the 5 nearest neighbors and their distances.

ANN.h:
- toggled off allowing same point to be a NN, i don't think will come up, but just in case

Makefile:
- added ANN to libs/include

scvt-mpi.cpp:
- added ANN header inlcude
- added variables for ANN arrays and such
- copied fns from ANN sample code readPt/printPt
- added fns to initialize ANN arrays, startANN()
- added fn to read ddpoints into ANN array, readDDPointsANN()
- added fns to create GS points to interpolate onto, makeGSPointsForANNQuery()
- added fn which will interpolate from ddvals using kdtree and gs points, createDDInterpValues()
- invoke all the ANN related fns on the master proc in main, near the start
Implemented a density function which uses a weighted sum of density values nearby the point where density is requested. The density values used in the weighted sum come from an interpolation of input data. Here the density information is computed on every processor, but there is certainly room to optimize this (split density array up by proc/region).

scvt-mpi.cpp:
- implemented IDW using ANN to do the NN search in both density() and createDDInterpValues()
- created another kdtree for use in density lookups
- moved ann/density stuff to main, no pid restriction

SaveDDValues:
- updated example to fix range error