Eeschema: allow dragging of text

Text doesn't have "special" handling of dragging, like connected items (it's
basically just a move).  However, allowing "drag" to work on text makes
handling text consistent when dragging other items.

eeschema/sch_collectors.cpp

@@ -143,6 +143,7 @@ const KICAD_T SCH_COLLECTOR::DraggableItems[] = {
     SCH_HIERARCHICAL_LABEL_T,
     SCH_COMPONENT_T,
     SCH_SHEET_T,
+    SCH_TEXT_T,
     EOT
 };
 

eeschema/schedit.cpp

@@ -1175,6 +1175,7 @@ void SCH_EDIT_FRAME::OnDragItem( wxCommandEvent& aEvent )
     case SCH_GLOBAL_LABEL_T:
     case SCH_HIERARCHICAL_LABEL_T:
     case SCH_SHEET_T:
+    case SCH_TEXT_T:
         m_canvas->MoveCursorToCrossHair();
 
         if( screen->m_BlockLocate.GetState() == STATE_NO_BLOCK )