General update to logging.

Make all loggers inherit from pyclaw logger.
Add convenience function for setting console logging level
in controller (h/t @ahmadia).
Provide alternative code for Python < 2.7, which doesn't handle dictionary construction
Check explicitly for sys.version_info >= (2,7)
Merge pull request #383 from rjleveque/util_dictionary

Alternative code for older Python versions
Merge pull request #382 from ketch/logging_update

General update to logging.
cell centers with ghost calculates correctly
correction to c edges and c edges with ghost
Merge pull request #384 from sanromd/ghost_cell_fix

Ghost cell fix
Make reading of petsc output files backward-compatible.
Merge pull request #386 from ketch/bugfix-io

Make reading of petsc output files backward-compatible.
Create a dictionary for CFL desired and max and check if are set.
Making dictionaries in sharpclaw private.
Always create attribute solver.num_eqn.
Merge pull request #388 from ketch/bugfix-solver_num_eqn

Always create attribute solver.num_eqn.
Fix values of CFL desired and CFL max for classic and sharpclaw's time integrators.
Merge pull request #387 from hadjimy/linear_multistep_methods

Linear multistep methods
Allow writing to gauges when num_aux = 0.
Merge pull request #390 from ketch/gauges_without_aux

Allow writing to gauges when num_aux = 0.
added hdf5 and netcdf write/read to petsc + usage example on 2d acoustics
Merge pull request #392 from sanromd/petsc-hdf5

 hdf5 and netcdf write/read support in petsc io + example