added files QmitkHistogramJSWidget.cpp / .h, Histogram.css /.js /.html and d3.v2.js

Added new WebView in QmitkStatisticsViewControls.ui to display a Histogram
based on JavaScript.

QmitkHsitogramJSWidget: shows a demo histogram, implemented variable size to
the histogram, so it fits to the size of the widget and there are no scrollbars shown.