Compute total number of working groups and assessment reports
Display 100 authors instead of 10
Use only 2 spaces of indent in new block of code
Assign charts updated to use IPCC data to the group "ipcc-authors"
Display all authors in the table, grouped by total assessment reports
Replace magic number 4390 with variable total_authors
Add 's' in totalAssessmentReportsChart variable name
Reset only charts in group 'ipcc-authors' from dc-data-count link
Compute total_authors from crossfilter's authors.size()

This is more explicit than using data.length.
Introduce utility function getter() to replace repeated pattern

The following pattern is used repeatedly in parameters of dc.js and
crossfilter methods:

    function (d) {
      return d.property_name;
    }

The new utility function allows to obtain the same function
more succinctly:

    getter('property_name')
Display bar chart of Total Assessment Reports

The chart allows to filter authors based on a range of
total assessment reports.
Use a logarithmic scale for the number of authors for each total AR

For some reason, no bar gets displayed with this scale.
Revert to linear scale for total authors

This is not ideal: no bar is visible for total AR = 5.
Increase height of bar chart to get a visible bar for total AR = 5
Move Total Assessment Reports Chart to the left
Shift graduations to the middle of bars in Total AR Chart

The actual implementation consists in shifting the whole chart by 0.5
and adjusting the values displayed in the filter range selector.
Use 'ipcc-authors' group in reset filter of Total AR Chart
Change title from "MEDEA Authors" to "IPCC Authors"
Add row chart with number of authors in each Cumulated Working Group
Define the color of each cumulated working group

The colors Red, Green and Blue are assigned to WG I, III, and II.
The color of other cumulated working groups is computed as the
sum of the colors of the component groups.