Merge pull request #3203 from takluyver/cell-magics-wholecell Separate InputSplitter for transforming whole cells This allows cell magics to include blank lines once again (closes #3178). InteractiveShell now has two input splitters: - `input_splitter` is used to determine when a block of input is complete, so you can use a cell magic in the terminal by leaving a blank line at the end. - `input_transformer_manager` is used to transform whole cells, so cell magics affect the whole of their cell. I removed the similar concept of 'input modes' for InputSplitter, because it was bound to get conflated, and it made the code rather hard to follow.