Column limit in output of notebooks

Just like there is a row-limit on the displaying of DataFrames, there should be a configurable limit on the number of columns that are displayed. Notebooks (like [this](https://github.com/Kotlin/dataframe/blob/static-examples2/examples/notebooks/json/KeyValueAndOpenApi.ipynb)) simply become to large to be viewed/uploaded to GitHub, especially after [enabling static output](https://github.com/Kotlin/dataframe/pull/511).
This limit can probably be a lot larger than the row-limit, but might have to include some visual cues that the rendered DataFrame is truncated.