Remove jumpkeys feature and add custom buffer shortcuts

This feature replaces the 10 "jumpkey" shortcuts (and the shortcuts for
setting them) with arbitrary buffer shortcuts and a UI to set them,
either by right clicking on the buffer and selecting "Set shortcut", or
from the Shortcut Settings page.
Add shortcut to change the shortcut of the current Buffer

Also move the BufferShortcutPopup to its own file so it can be
instantiated from mainwin.cpp. Change the behaviour of the popup so that
you can start typing a shortcut immediately after clicking the menu item
or typing the shortcut.
Add a "print" command to only display an info message, without sending anything to server
Merge branch 'tempbranch' into personal
Merging in Hot Keys