Copy paste entire cells

[fonsp]

@ekzhang

Right now you can select multiple/single cells, but you can't copy paste them:

It needs to work among different notebooks! And if possible, different notebooks from different sessions (e.g. one on binder, one running locally).

Maybe you could think about the contents of the clipboard? Some options:

1. It doesn't matter, you put the data in localStorage. But then it only works within the same session
2. The copy data is exactly like it is in the file (i.e. # |==\ncode\n\n ish). And when you paste onto the page it recognizes that format (and generates new cell IDs to avoid duplicates). This is cool, because people often post notebooks in that format on github.
3. The copy data also contains formatted output? Like what happens right now if you text-select and copy+paste to Google Docs.

Another thing: for this you would want to place a superbig text cursor after a cell or between two cells, before you hit Ctrl+V. I think this could be really cool, if you also allow text input to create a new cell.

[fonsp]

Also, because we have a reactive notebook, it would be nice if Ctrl+X would not immediately delete the cells, but wait for you to paste it, and then move instead. Just like in excel, or in the windows file manager. This prevents two reactive runs.