New features

• New APBS tutorial
• New tools/python/vgrid/mergedx.py script to merge dx files generated from parallel APBS runs back into a single dx file.

Bug fixes

• Fixed bug in parallel calculations where atoms or points on a border between two processors were not included.  Modified setup algorithm for  parallel calculations to allow partitions in order to obtain grid points and spacing from the global grid information.
• Modified extEnergy function to work with parallel calculations, giving better accuracy.