Rearrange examples

1. Remove `basic_demo.py` in favor of `features.ipynb`
2. Remove the old julia-set example
3. Remove `make_distarray.py` and all of the `plot_`... examples.  They're only like 5 lines and all eclipsed by `features.ipynb`.
4. Put the `plot_distarray_protocol` stuff in its own folder.
5. Rename the remaining example folders to use underscores instead of dashes for uniformity.