Simpler multiple REPLs

[ksixty]

It would be nice to be able to open a second REPL by doing something like C-u M-x julia-snail.

Per-project setup is not so good when you need to test a thing or two quickly in a disposable session.

[gcv]

Patches welcome. :)

[MasonProtter]

In addition, having to come up with a unique port and unique buffer name is especially painful. Not sure what the regular way is to get C-u M-x julia-snail working, but I guess we just need it to automatically generate a buffer name, and a unique port number?

Are there any considerations for what constitutes a valid port entry here, and are there port ranges we'd need to try and avoid because they're used by other processes? (e.g. like with SSH it's hard to a-priori generate a free port number)

[gcv]

We can probably auto-guess a reasonable buffer name based on the containing project name (seems doable using project.el, but I didn’t verify). I don’t know about ports, but I haven’t run into much trouble using 10011, so Snail can potentially track which ports it has already used in the 10011-10100 range and allocate from there.