Plots to be included in the first version

[pnezis]

The following plots should be included in the first version:

Single view plots

Check the items once the plots are fully implemented and documented

• [x] line
• [x] barchart
• [x] countplot
• [x] scatter
• [x] bubble
• [x] histogram
• [x] heatmap
• [x] density
• [x] stripplot
• [x] area
• [x] pie
• [x] donut
• [x] boxplot

Composite plots

• [x] pairplot