CVS commit by aseigo: 

enable dragging on all buttons (Ctrl or Shift + Drag on menus, for obvious
reasons =)

centralize the dragging code into PanelButton to make behaviour consistent
(e.g. drag threshholds, icons)

to make a button NON draggable between panels (why?) or to do something
special prior to a drag just override the protected startDrag() method in
PanelButton


  M +1 -0      desktopbutton.cpp   1.14
  M +84 -17    panelbutton.cpp   1.14
  M +11 -2     panelbutton.h   1.12
  M +5 -33     servicebutton.cpp   1.26
  M +1 -5      servicebutton.h   1.6
  M +8 -31     urlbutton.cpp   1.18
  M +1 -5      urlbutton.h   1.5