Qt: Update and rename the summary dialog.

Go back to a single view similar to the GTK+ UI. Apply layouts using Qt
Designer.

Rename the menu item and class to "Capture File Properties". It's not
really a summary if it contains details such as "marked average bits
per second". We might want to move this to a "Properties" item under
the "File" menu similar to other applications.

Add the GTK+ summary icon (for now) to the toolbar and open the
properties dialog on clicking.

Singleton dialogs delenda est[1]. Let the user open as many summaries on
as many capture files as he or she wishes. Also, global cfile delenda
est[2].

Don't blindly include QtGui. Add specific components instead.

Use consistent method names, variable names, and patterns. Try to
document what "consistent" means.

Adjust the way we display some statistics to match the summary bar, e.g.
displayed = captured if we don't have a filter applied.

[1] Not really.
[2] Yes, really.

Change-Id: I11793b1d79dd0c3f70414ac8592b86181da59916
Reviewed-on: https://code.wireshark.org/review/5274
Reviewed-by: Gerald Combs <gerald@wireshark.org>