Incorporate the `GaugeSolution` class fully into PyClaw

[mandli]

Replace the current gauge functionality in PyClaw with the new class that the Fortran code is also using.

[mandli]

One thing I think we may need to implement is to buffer output and dump it out to disk periodically. The current functionality will write to a file immediately (or at least until the file buffer decided to dump it out) so if there is a crash or some similar interruption all the gauge data to that point is hopefully on disk. The most obvious implementation in PyClaw would be to simply place the gauge output into the q array but this would need to be saved periodically somehow. In other words we need to implement a buffering capability somehow.