Qt: Resolve duplicate keyboard shortcuts

Qt: Resolve duplicate keyboard shortcuts

Two Edit->Copy methods are using the same keyboard shortcut as other
functionality:

1. Ctrl+Shift+D is used for "Copy this item's description" and
   "Ignore All Displayed packets"

2. Ctrl+Shift+F is used for "Copy this item's field name" and
   "Reload as File Format/Capture"

Resolve this by changing the Copy methods to use Ctrl+Alt+Shift as modifier.
Add a keyboard shortcut for "Copy all visible items" while here.

Change-Id: I0d963501055e63963d93e211f592aa9e82801d3c
Reviewed-on: https://code.wireshark.org/review/24884
Petri-Dish: Stig Bjørlykke <stig@bjorlykke.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>