Minimized calculations for adding PSF component to raw array. lanczos3 and bilinear kernel weights are now both calculated only for the relevant pixels (not the whole array, as lanczos3 previously did). Also unified the method used.
Fixed a bug in PSF timing calculation. Previously was re-calculating and re-allocating coordinate arrays on every iteration. This step made up the bulk of the measured time for each iteration. Changed so it is pre-calculated once, as happens in the fitting code.