This avoids issues with having a single PyGILState_STATE that can
get into issues. Its better to let Python manage that.
The original problem with hanging on recsursive async calls is
solved using a single local PythonGIL object to record the state at
time of manually locking/unlocking.

- Renamed to ProcessingAlgorithm
- Also renamed ProcessingAlgorithmBase.

- Renamed to PreprocessingAlgorithm.

- Removed DataProcessor from the names of:
  - DataProcessorOneLevelTreeManager
  - DataProcessorTwoLevelTreeManager
  - QDataProcessorOneLevelTreeModel
  - QDataProcessorTwoLevelTreeManager

- Renamed to PostprocessingAlgorithm.

- Renamed to SaveTableAsCommand

- Renamed to PasteSelectedCommand

- Renamed to OptionsCommand.

- Renamed to OneLevelTreeManager

- Renamed to ImportTableCommand.

- Renamed to ExportTableCommand.

- Renamed to ExpandGroupsCommand

- Renamed to DeleteGroupCommand.

- Renamed to CutSelectedCommand.

- Accidentally renamed usages of DataProcessorCommandAdapter to
CommandAdapter rather than QtCommandAdapter. This commit fixes that.

- Renamed to CopySelectedCommand