pyicon/pyicon_tb.py: Fixed bug in level interpolation (calc_vertical_interp_weights and zonal_average_atmosphere). New function nctime_to_datetime64 to calculate numpy.datetime64 objects from netcdf time.

pyicon/pyicon_tb.py: Changed radius_of_influence and convert np.nan in apply_ckdtree to masked values everytime (this was prob a bug before).

  * a bit of rearanging routines to get a more logical order
  * new intermediate function: ckdtree_points to calculate grid points
  * new function: calc_north_pole_interp_grid_points for a more
    appropriate grid for polar projections
  * new functions: spherical_to_cartesian and cartesian_to_spherical
  * splitting: mask_big_triangles

  * time_average: Added option to give list of indices over which should
    be averaged.
  * identify_grid: Added atmosphere r2b4 grid.

pyicon.quickplots: Adapted to new arrange_axes and adapted to splitting and moving of quickplot related functions to quickplot module.

Moving pyicon_quickplots and pyicon_view to their specific directories. Adding imports in __init__ files. Moving qp specific functions from pyicon_tb to pyicon_quickplots.py

pyicon_tb.py: Removed calc_bstr and IconVariable which was moved to pyicon_calc and pyicon_IconData.

  * exclude aplly_ckdtree_base from apply ckdtree
  * new: interp_to_rectgrid
  * calc_moc and zonal_average_3d_data: new basin: indopacso
  * new: nctime2numpy
  * get_timesteps: go through every file and concatenate time steps
    instead of allocating array first and assume same number of tsteps
    in each file
  * 1st version of edges2cell
  IconData:
    * new options: omit_last_file, time_mode
    * fpath_tgrid=='auto': take grid file from pool directory
    * if search_str=="": no search is done
    * new: reduce_tsteps
    * more variables loaded from fx file
  * shade: new option draw edges
           cbticks can be array of colorbar ticks

  * identify_grid: Added atmosphere r2b9 grid: r2b9a: icon_grid_0015_R02B09_G
  * IconData.load_vgrid: added more vert. grid variables
  * IconData.load_tgrid: added cell area

  * reading also coordinate types in zonal_average
  * option to decide whether cgrid, egrid or vgrid should be read in ckdtree_hgrid
  * new function load_hsnap
  * new mode to read time units of netcdf file in get_timesteps
  * coordinate type (clat, vlat, elat) can be passed to IconVariable
  * pyicon.shade only sets title of cbar if cax!=0

  * gname meta data can be passed to ckdtree
  * use_tgrid in hplot_base can be parsed from IcD object
  * more options to pass info about path and fpath data e.g. for fx files
  * load_grid is split into self.load_tgrid self.load_rgrid and self.load_vgrid
  * fpath_html insted of fname_html allows to specify full path of qp website html file

Added:
  * zonal_average_3d_data
  * zonal_section_3d_data
  * print_grid_info

Changes:
  * qp_vplot: do_load_moc -> mode_load with more possible options to load 2d vertical data
  * qp_vplot: allow for plotting zonal averages
  * QuickPlotWebsite: info line and path

Bugs:
  * vplot_base: xaxis can be chosen by xvar argument

added:
  * zonal_average
  * load_moc
  * qp_hplot (qp_hor_plot is removed)
  * qp_vplot

expanded:
  * added cincr to hplot_base and vplot_base
  * added cmap conversion to hplot_base, vplot_base
  * added some of cartop features to hplot_base
  * made vplot nicer
  * cincr and norm in shade and trishade

changed:
  * IconData __init__: use_tgrid is inferred from rgrid_name
  * IconData __init__: added some checks
  * QuickPlotWegsite add_fig: fpath instead of path_pics+fname
  * colorbar ticks in shade and trishade related to disrcrete color map

  - icon_to_regular_grid
  - apply_ckdtree
  - ckdtree_hgrid
* added function to interpolate to section:
  - icon_to_section
  - ckdtree_section
  - haversine_dist
  - derive_section_points
* made it possible to scan through time steps within a single cdf file:
  - get_files_of_timeseries
  - get_varnames
  - get_timesteps

  * Added TOC at top of file with new ideas for functions / objects
  * Added new function identify_grid
  *                    load_tripolar_grid
  *                    crop_tripolar_grid
  *                    crop_regular_grid
  * Added new class IconDataFile that should be used for QuickPlots
  * Added function qp_hor_plot for Quick Plots
  * Added class QuickPlotWebsite for generating a Website of QuickPlots