Added a scatter plot widget class with some code for interpolating heatmaps
Added some heatmap code to scatterplot
Removed prints from scatter plot
Merge branch 'master' into heatmap
Added to_sql() for DiscreteVariable.
Added (the mysteriously disappearing) icon for BoxPlot
Added sql versions of EqualWidth() and EqualFreq().
Merge branch 'master' into heatmap
Reverted test sql base to master version.
Modified stored procedures for discretization. Modified to_sql() in DiscreteVariable.
Pass domain as parameter to find_or_create_context.
Added basic heatmap widget
Merge branch 'master' into heatmap, to update boxplot.
Merge branch 'master' into heatmap
Do not try to send signals with no signalManager.

When widgets are run without canvas, they lack signalManager.
Fix method call.
Provide default value to avoid AttributeError.
Use different location for settings (so they do not clash with orange2).
Allow tooltips on toolButtons.
Fix a contingency indexing bug.

contingency['iris', 'iris'] worked, while contingency['iris']['iris']
failed. The second form of indexing is used in parallel coordinates
widget.