Clarify "session" vs "notebook"

[sdball]

On the Livebook homepage there's a button for "New notebook" but then the list of running notebooks is noted as "Running sessions". It'd be nice if the button and list header aligned. Either "New session" or "Running notebooks"

To me "New session" makes more sense as a I think of a session as a running Livebook instance that may or may not be backed by a file. And I think of a notebook as a file that may or may not be open in an active session.

[josevalim]

I think it makes sense. At the beginning the term sessions was more prominent but now not as much. If we do this, we should probably rename the bulky actions to "Disconnect" and "Close":

[jonatanklosko]

@josevalim we use the wording session in several places, including "session secrets", multi-session apps, urls (relevant for proxy). I still think the distinction makes sense and is intentional.

The button could be either "New notebook" and "New session", since I think both are true. But "New notebook" is consistent with "Open notebook", "Fork notebook", all of these create a session, it's just that in case of "New notebook" the session starts from an empty notebook. Also, given that it's probably the first button that a new user would click, "New notebook" is likely more meaningful to them.

So in summary, I like both "New notebook" and "Running sessions". The bulk action should say "Close" though, because that's what the individual menus say as well. I pushed the update to main.