gnc.py
1. add method _set_map_title_unit_by_mapvarname
2. unit_func has been applied twice in gnc.Ncdata.Add_Vars_to_Dict_by_RegSum,
   now this has been corrected.
Pdata.py
1. classmethod "from_dataframe" added for Pdata.Pdata,
   original Pdata.from_DataFrame will be decprecated.
2. Add "from_dict_of_dataframe" for Pdata.NestPdata
3. classmethod "merge_mdata" added for Pdata.Mdata
gmapkw added
correct the bug in missing_value,_FillValue setting in gnc.NcWrite
add slicing function; set_new_tags for NestedPdata
addd gmapkw
add import Iterable
a series of changes
add plot levels in cons.py
Add pseudo axes in the Pdata.set_legend
Add atumatic check of time_length and PFT in the gnc.nc_spatial_concat_ncfiles
Add new functions:
1. _cm_contrast_2cmap and cm_contrast_red2green for makding
  unsymetric contrasting cmap
2. change Set_Cbar_Label_Parallel to colorbar_set_label_parallel
3. Axes_get_bounds for a group of axes
4. _get_axesrec_by_pos_offset and Axes_add_axes to add new axes
  in relative to a group of axes
Add in Pdata.Mdata and bmap.py
the show_colorbar keyword to allow suppressing of colorbar in
mapcontourf
add more biomass levels in different units
minor change in documentation of gnc.Ncdata.get_pftsum
add keyword middle in Axes_add_axes in g.py
add pleg_merge method
1. add Axes_adjust_position in g.py
2. add set_new_tags method in g.ProxyLegend
add interp_level method
add colorbar method in bmap.mapcontourf object