Fix data file writing bug

Occasionally when data files were being written out in the same process as
a run the buffer for each of the files were never being actually dumped into
the files themselves leaving emtpy files.  The call to `self.close_data_file`
is added in this commit to all the data objects that are missing it.
Remove maxmx from set_storm_fields
Add contourf plot convenience function
Add storm surge support for contourf plotting
Files to keep track of max flow depth, velocity, arrival times, etc.  copied from rjleveque's version of geoclaw 4.x.
Renamed fgmax_* to avoid conflict with old fixedgrids module.
Indices have not yet been reordered so more work needs to be done before it can be tested.
reordered indices in fgmax routines, starting to test.
Runs but have not yet plotted results
moved fgmax routines from src/2d/ to src/2d/shallow
change input file to fgmax.data
fgmax: Removed unused parameters related to output times, since only max is supported
added dev/ directory and dev/bowl-slosh_fgmax with test code for fgmax capabilities
fgmax option modified to allow multiple files for multiple fgmax grids, specified in setrun.py...
Modified fgmax_read and added set_fgmax for consistency with style of fixedgrids, etc.  Modified data.py to parse and create fgmax.data file giving list of file names.
Fixed error test for missing dtopo file
fixed typo in fix to DTopoData
fixed make_fgmax.py to not print number of grids
fixed error in previous fix to data.py
dev/chile2010_fgmax added to test fgmax for coarse grid on ocean - revealed problems...
interpolating h and B separately can lead to large h and B>0 for points interpolated between ocean at rest and high onshore topo.
Arrival times looks at h > FG_HARRIVAL which is ok onshore but not in ocean.
Will try different approach.
fgmax - new approach where values(1) contains eta tilde...
= h+B where h>0 or sea_level where h==0.  This works better for interpolating at points near the shoreline.
changed tick.f to give more info about ntogo errors
fgmax modifications to make min_level_for_arrival and arrival_tol variables for each fgrid...
Improved plotting routines to plot arrival time contours on zeta max plots.
Fixed various other things.
Cleaned up geoclaw/examples for use in the gallery, and added fgmax routines to Makefiles.