Show more on events in info widget

[cbrnr]

Partially addresses #329.

This changes how events are shown in the info widget:

• The total number of events is always shown
• If there are fewer than 8 unique event types, the count for each type is shown in parentheses.
• If there are between 8 and 12 unique event types, only the unique event types are shown in parentheses.
• If there are more than 12 unique event types, only the first 6 and last 6 unique event types are shown in parentheses (with a ... in between).

To completely implement #329, there needs to be an option which shows the counts of all unique event types (in addition to the total count). Maybe in the "Events" dialog?