Set the compression flags even if --compress was not explicitly called; set default to true too
1. Set a maximum number of bad-file checks and warnings, per filetable. The maximum is 2.
2. The former basic_filetable.list_variables() had returned only real variables.  Recently
I had changed it to also include axes.  Now we have two methods, one for each:
list_variables() is the old one, and list_variables_incl_axes() is the new one.
I also exluded axes from list_variables_with_leelaxis but not from has_variables.
fix a tiny typo in a comment
In reduce_time(), replace hasattr(ax,'bounds') with a test on whether ax.getBounds() is None.
This deals with the case where ax has the bounds attribute but it's a lie - the variable named
in the attribute doesn't exist.
Replace filetable.list_variables() with filetable.list_variables_incl_axes, because sometimes
we need to treat an axis as a variable.
For plot set 13, replace filetable.list_variables() with the new method
filetable.list_variables_incl_axes() as this plot set needs to get axes that way.
Add a test of plot set 13.
Make sure not to try to compute climatologies for variables not named by the filetable's
list_variables() method.
Clean up some error messages paths and directory creation issues
delete obsolete comment
Ad-hoc special-case treatment of QFLX in kg/m2/sec.  This may be changed later!
I left in some debugging prints for near-future use in other units work.
Finally, the choice of units to convert to is changed.  It was (when preferred_units
is unset) always the first variable.  Now it's whichever variable has numbers most O(1).
Add another example, some cloud variables.
Fix number_of_diagnostic_plots which no longer was returning a meaningful number.
But also it no longer returns the number of sets of .nc files written out.
Now it's the number of vcanvas2.png() calls.  That's the number of "summary plots".
bugfix: when a variable's units were changed, I had updated varmax but not varmin.
Now varmin is updated too.
Also I left in some debugging code which will be useful in near-future units work.
Merge branch 'devel' of github.com:UV-CDAT/uvcmetrics into devel
Two special-case treatments to allow CERES data: (1) reduce2scalar_seasonal_zonal
recognizes and changes its weird time units, (2) reduced_variable.reduce()
calls a new function special_case_fixed_variable to convert a CERES variable with
a nonstandard _FillValue attribute into a proper masked variable.

Moreover, reduce2scalar_seasonal_zonal ignores a time axis which consists of only
one missing value.  We have encountered this kind of (non-CF-compliant, malformed,
and just plain silly) data too many times.
Delete two debugging printouts.
Only call vcs.init() one time, outside the main loop. Seems to work ok in testing
New file clouds.py to support creation of cloud variables.  They are distinguished in that
each variable and its axes have names which depend on the obs you will compare with.
Many new cloud variables in standard_variables.  Their cloud-related axes also are put
in an exclusion list in plot set 5.  And a one-step recursion is added to stdvar2var(),
necessary because of the use of name translations before computations of cloud variables.
Finally, I deleted a few debugging print statements.