Refacto of the scene cut detection, make it generic and add another algorythm as an option

operators/spreadsheet.py

@@ -355,7 +355,9 @@ class VSETB_OT_import_spreadsheet(Operator):
         #print(SPREADSHEET[:2])
 
         cell_types = project.get_cell_types()
-        cell_names = {k: spreadsheet.cells[k].import_name for k in header if k}
+
+        header_enabled = [x for x in header if spreadsheet.cells[x].enabled]
+        cell_names = {x: spreadsheet.cells[x].import_name for x in header_enabled if x}
 
         #separator = spreadsheet.separator.replace('\\n', '\n').replace('\\t', '\t').replace('\\r', '\r')
         
@@ -364,10 +366,12 @@ class VSETB_OT_import_spreadsheet(Operator):
         frame_start = scn.frame_start
         for row in SPREADSHEET[1:]:
             #print(row)
-            cell_data = {cell_names[k]: v for k, v in zip(header, row) if k}
-            #cell_data = {k: v for k, v in zip(header, row)}
+            cell_data = {cell_names[k]: v for k, v in zip(header, row) if k in cell_names}
             shot_name = cell_data['Shot']
 
+            if not shot_name:
+                raise Exception()
+
             #strip = next((s for s in sequencer if s.vsetb_strip_settings.source_name == shot_name), None)
             strip = next((s for s in shot_strips if s.name == shot_name), None)