[Poshuku] Removed useless #include.
[Otlozhu] Set new comment only if it's changed.
[Otlozhu] Added EditCommentDialog for #1601.
[Otlozhu] Use multiline editor for comments.

Closes #1601.
[Otlozhu] Add "Add todo" button to the ctx menu for #1602.
[Otlozhu] Clone action.

Closes #1602.