Fixing PISM parameter names (Paterson-Budd_*) to remove hyphen, to get CF compliance.

This minor problem arises because pism_config is now included in output files.

The CF convention document excludes hyphens:  "Variable, dimension and attribute
names should begin with a letter and be composed of letters, digits, and
underscores. Note that this is in conformance with the COARDS conventions,
but is more restrictive than the netCDF interface which allows use of the hyphen
character."
Add _flux to standard name for climatic_mass_balance.  See 995aac.
Cleanup.
Forward-declare "IceModelVec" in PISMVars.hh.
Fix a doxygen comment.
Add "_flux" to land_ice_surface_specific_mass_balance.
Add Egholm references.
Remove the "PISM" prefix in the source code browser.
Add the "long_name" attribute to pism_config.

Also: rewrite the script that generates tables of configuration parameters.
Close #99.

Now enthalpy and temperature time-stepping code computes the *grounded*
basal melt rate, which is combined with the shelf base mass flux
provided by an ocean model in IceModel::combine_basal_melt_rate()
(possibly using the fractional floatation mask computed using a sub-grid
parameterization of the grounding line position).

Oce IceModel::combine_basal_melt_rate() is called, the rest of PISM can
use IceModel::basal_melt_rate in both grounded and floating areas.
Whitespace changes.

(I had "git diff" set up to ignore whitespace changes, to I did not
notice that I pushed a commit with the code indented in this funky
way.)
Enable scalar precipitation multiplier. See #271.
Allow setting the output size without command-line options.
Remove an unused variable.
Minor cleanup in PA_frac_P. See #271.
allow fill_missing.py to handle files with a time dimension. Should this be considered a bug fix that needs to go into v0.61?
Fixed fill_missing.py
Remove a redundant comment.
Make sure that ks is always valid.

'ks' is the index of the top-most fine vertical grid level that is still
in the ice.
Document new modifier PA_frac_P. Close #271.