Bar plot maintenance

[dv-usama-ansari]

Coming from #563

Please see comments for more details

[dv-usama-ansari]

#563 (comment)

Spacing between axis label and ticks

[dv-usama-ansari]

#563 (comment)

Clipped tooltip for very wide graph

[dv-usama-ansari]

#563 (comment)

Missing legend

[dv-usama-ansari]

#563 (comment)

Bar plot for a group column containing all null values for this session:

Discussion with @thinkh: We should show #71787E Unknown item in the legend and the tooltip

[dv-usama-ansari]

#598 (comment)

When all the values of an aggregation are 0 (not null or undefined), the bar chart does not show up since it cannot plot bars with 0 width. This happens for the following combination of configuration:

Me and @thinkh discussed came to a conclusion that there is unfortunately no way to show a bar with zero width. We should show a message to the user in such a case and prompt him/her to change the aggregation type or column selected

[dv-usama-ansari]

Comments with @thinkh following the discussion of #596 (comment):

-Survival months filters out the 0 for all the aggregation.

• Show 0 for all the aggregation other than count.

-Tumor size has null across all categories of breast surgery type

• Filter out null and the non-null-minimum is the minimum value

• Add documentation for decisions made