[PD] allow expression for pocket offset

- also disable KeyboardTracking for some fields to avoid unnecessary and often time consuming recomputes while typing in

src/Mod/PartDesign/Gui/TaskPocketParameters.cpp

@@ -126,6 +126,7 @@ TaskPocketParameters::TaskPocketParameters(ViewProviderPocket *PocketView,QWidge
     // Bind input fields to properties
     ui->lengthEdit->bind(pcPocket->Length);
     ui->lengthEdit2->bind(pcPocket->Length2);
+    ui->offsetEdit->bind(pcPocket->Offset);
 
     QMetaObject::connectSlotsByName(this);