[FEATURE] - Save functionality for the ListView of each tab

[creizlein]

From sMkTaskManager created by creizlein: creizlein/sMkTaskManager#7

Description of the feature, modification, idea or suggestion

Add a new File/Save and File/Save as... Menu items that will allow to save the currently displayed listview content to a CSV or a TSV file.

Proposed implementation details (optional)

Since File menu is general for all tabs, In order for it to be enabled we can rely on whatever that active tab has a ListView property != which is already declared on the iTaskMaangerTab tab.

I think the file should include a generic header with at least the timestamp.
When you hit Save second times it should append to the already saved file, not overwrite, right?

Additional context or screenshots (optional)

No response