Improvements to visualisations

[ghost]

• Add more visualisation types
• Make the visualisations more feature-complete

[JimmeeX]

Currently, the visualisation interface is very limited in functions, features, and interactivity.

It would be great for the teaching staff to analyse and visualise their data (from datalabs) to learn about the distribution of the course cohort with respect to certain fields (eg, distribution of marks for an assignment) and interactively select a subset of that data to perform an action (eg, send email to students with low assignment marks).

Some sample features may include Filtering (or including/excluding)

• Click & Hold rectangular selection of multiple data points, and click "Filter" shown in a tooltip to include or exclude that data subset.
• The ability to select multiple data fields (maybe by holding shift or ctrl), and clicking "Filter" like in the previous point.

More Plots Currently, only Bar plots and pie charts are available. Some other commonly used plots may include:

• Histograms (distribution of a numerical column)
• Scatter Plots (two numerical columns)