1) Update of the Double Mach Reflection problem (in run/Hydro/Hydro-2D/DoubleMachReflection) to fix the boundary conditions. This is not a fix of the code, but rather a fix of the test problem parameter file to go from periodic BCs everywhere to partially periodic, partially inflow (which is what it should be). I also added a plot script to this test problem.
2) Made a very small fix to enzo.C to ensure that the '-g' option (the "Write gravitational potential only" option) works. It's not clear that this has ever worked in Enzo 2.x, interestingly enough.