bar charts polished...* fixed bar chart width (two bars were invisible)
* disabled basic stats update effects, if they are not visible
* fix: unchecked samples were shown in charts
(because attr('checked') was used instead of prop('checked'))
* bar chart gets redrawn after checkbox changes
* edit_data_change is also called when clicking buttons
from the 'Block samples' panel
* better bar chart transitions (use sample name as d3 key function)
improved legend...Now the legend is always positioned on top, so that no overlapping
with the plot occurs and it's always visible.
The legend is now composed of spans, not an SVG anymore.
Also increased the legend font size to 20px.
fix attribute coloring...also I found out that there are two legends shown simultaneously,
but one is suitable only for discrete values, and the other for
continuous; now only the suitable one is shown
