Refactor of topotools testing suite.

Includes a number of improvements to the tests including the use of temporary
directories, removing extraneous code and the removal of the dependency of
running the test_against_old when only the old version of the topotools
were present.
Move test data to data subdirectory
Bug fix for unarchiving
Add back better test descriptors
Slight refactor of dtopo tests
Add stubs for next test additions
Move distance related functions to util module
Remove repeated functionality and fix bugs

Removed functionality includes the distance utility functions, the common
task of trying to guess a topo type from a file's suffix, and moving most
of the constants to util so they are not calculated multiple times.
Refactor some of the existing functionality

Mostly an attempt at tightening up some of what is already here.  Also adds
some documentation and adds an `axes` argument to many of the plotting
routines.
Merge remote-tracking branch 'rjl/dtopotools2' into dtopotools2

Conflicts:
	src/python/geoclaw/dtopotools.py

Merge simultaneous updates to adding axes and figure keyword arguments.