Update dataset preview page

[hjwilli]

Update the dataset preview page with more data analysis plots.

(Notes from our initial pass at this are in issue #209, in particular some ui ideas are here https://github.com/EpistasisLab/pennai/issues/209#issuecomment-503251165 )

[nupurbaghel]

All changes can be seen on the data-preview branch.

A list of the new components / changes to existing components is as follows:

• DatasetTabbed : Contains 3 tabs.

  1. The Preview tab contains the original data preview content (Dataset component)
  2. The Basic Stats tab contains newly added Plotly graphs (DataStats component)
  3. The Sample tab contains sample plots using custom test data (code can be seen in the parent component i.e. DatasetTabbed component)

• DataStats component :

  1. Modifies data from row-wise format received from Papa parse to column-wise format (currently top 1000 rows are only selected for the graphs)
  2. Creates a list of categorical, ordinal and numerical features (slices to select first 20 from each category)
  3. Currently it only makes use of PlotlyBarPlot and PlotlyBoxPlot components.
  4. For future scope, we can separate data into multiple parts for each class and make use of PlotlyStackedBarPlot

• PlotlyBarPlot : uses histogram count method to generate histograms, can be updated to any other custom function (see example usage in sample tab)

• PlotlyBoxPlot : customized to stack one or more box plots (see example usage in sample tab)

• PlotlyStackedBarPlot : stacked histogram plot (see example usage in sample tab)