dataset is temporary

[Stephen-McDaniel]

Please:

• [X ] Check for duplicate issues
  DONE

• [X ] Describe how to reproduce the bug / the goal of the new feature request
  Add a dataset from a URL, https://gist.githubusercontent.com/Bondifrench/978f78f24c638546356af7610487c786/raw/28f0ef243f668630dfe676658b6d611d9170425c/InDDHeader.csv

Use it for some explorartion

Click Change (dataset), only the Vega samples appear, not the current dataset.
Refresh the window, the dataset has vanished.
find . | grep .csv finds no data on the server

So, is all data temporary via this dialog/process? Perhaps I am missing something,

• Provide an example spec in JSON and, if applicable, screenshots or GIF videos (e.g., using https://www.cockos.com/licecap/)
  2.0.0-alpha.24