Carriage return

Execute a carriage return on the currently-selected cell. If the cell is in a non-editing status, move cursor to the next non-empty, non-comment cell of the same line, or move cursor down to the next cell of the same column if there is no non-empty, non-comment cell in the current line; If the cell is in an editing status, accept the entering and move cursor to the next non-empty, non-comment cell of the same line, or move cursor down to the next cell of the same column if there is no non-empty, non-comment cell in the current line.