Created generalized point interpolation filter

This is a general framework to interpolate attributes from a data source, using the input as the set of interpolation points. It requires specifying an interpolation kernel (several of which have been created), as well as a locator for fast spatial searching. Although similar in concept to vtkProbeFilter, it does not interpolate using a cell's interpolation basis, rather it uses a local evaluation of the specified kernel, applied to the local points (neighborhood) around each interpolation point, to compute the interpolated data values. The algorithm is threaded with vtkSMPTools.