Discard history on project-file save/load (OpenShot#2468)

* Discard history on project-file save/load (OpenShot#2400)

* updates.py: add newline at end of file
* conversion: total_size() for data structs
* project_data: Log load and save operations

Believe it or not, in all the logging OpenShot does, never was the fact 
that a project file was being loaded or saved actually logged as such. 
Now it is, complete with the `file_path`.

* project_data: Discard history

On both load and save of project file data, any `"history"` in the JSON 
will be discarded, replaced with an empty struct:
`{ "undo": [], "redo": [] }`

Temporarily, while testing the feature, the total size of the data 
structure being discarded will first be computed and logged.
```
project_data:INFO Discarding history of size 105246892 bytes
```

* Removing logging of history size, since it does not serve much of a purpose. Soon we need to revisit this and try and improve the persistance of history (within reason to a few dozen changes perhaps), and ensure we don't allow nested histories (since history is an attribute of a project object).

src/classes/project_data.py

@@ -309,6 +309,8 @@ def load(self, file_path):
         self.new()
 
         if file_path:
+            log.info("Loading project file: {}".format(file_path))
+
             # Default project data
             default_project = self._data
 
@@ -337,6 +339,10 @@ def load(self, file_path):
             # Check if paths are all valid
             self.check_if_paths_are_valid()
 
+            # Discard history
+            log.info("Discarding history")
+            self._data["history"] = { "undo": [], "redo": [] }
+
             # Copy any project thumbnails to main THUMBNAILS folder
             loaded_project_folder = os.path.dirname(self.current_filepath)
             project_thumbnails_folder = os.path.join(loaded_project_folder, "thumbnail")
@@ -687,6 +693,8 @@ def save(self, file_path, move_temp_files=True, make_paths_relative=True):
         """ Save project file to disk """
         import openshot
 
+        log.info("Saving project file: {}".format(file_path))
+
         # Move all temp files (i.e. Blender animations) to the project folder
         if move_temp_files:
             self.move_temp_paths_to_project_folder(file_path)
@@ -695,6 +703,10 @@ def save(self, file_path, move_temp_files=True, make_paths_relative=True):
         if make_paths_relative:
             self.convert_paths_to_relative(file_path)
 
+        # Discard history
+        log.info("Discarding history")
+        self._data["history"] = { "undo": [], "redo": [] }
+
         # Append version info
         v = openshot.GetVersion()
         self._data["version"] = { "openshot-qt" : info.VERSION,

src/classes/updates.py

@@ -308,4 +308,4 @@ def apply_last_action_to_history(self, previous_value):
         """ Apply the last action to the history """
         if self.last_action:
             self.last_action.set_old_values(previous_value)
-            self.actionHistory.append(self.last_action)
+            self.actionHistory.append(self.last_action)