Line Chart: improve ticks on single date, multiple hours

[ajdapretnar]

Timeseries version

master since biolab/orange3-timeseries#220

Orange version

3.32.dev

Expected behavior

When the timeseries data belongs to a single date but to multiple hours, ticks should display only hours, i.e. 23:00.

Actual behavior

Ticks display the day + hour, which is quite unintuitive.

Steps to reproduce the behavior

NewLog3.txt File - Line Chart.

Additional info (worksheets, data, screenshots, ...)

This is not major. It only happens after a certain width of the widget. When shrunk, the widget displays only hours.

[janezd]

Moved from timeseries: the issue is in owscatterplotgraph.AxisItem's adaptation for time variables. The same problem would appear in the scatter plot.