Feature request: Integrate Pkg3 projects into Juno

[mkborregaard]

As discussed recently on Slack.

It would be nice to have Atom projects associated with the project structure of Pkg3.
That could involve just activating the Pkg project associated with that folder, e.g. by having --project flag on julia by default - it should simply default to (1.0) when no project is in the folder. This is nice because with Pkg3 you'd not necessarily have all the packages you use installed on your default project, so mostly you'd need to activate your project to use it anyway.

It would also be nice to have an optionin the Julia menu bar that allows you to “create” a project or “open” a previous one, that would take care of opening the right folder and activating the environment etc. According to Pkg documentation, all projects are "packages" or "applications", where "applications are e.g. simulations or analytical code not intended as a package. Applications should also have the default file structure with src/myproject.jl , test/runtests.jl and project.toml, and it would be nice to have these created automatically. Possibly PkgDev could be used for this. Possibly with an empty module inside src/myproject.jl etc, to support new adopters (and old adopters) having a good workflow in Julia.

[MikeInnes]

Having the --project flag on by default has the same issues as for Julia proper, unfortunately. There are probably ways to make this convenient but opt-in though; for example, having an "activate" command perhaps whitelisting any previously activated project for automatic activation.

[pfitzseb]

Similar thoughts in JunoLab/atom-julia-client#524.

[pdeffebach]

Similar to #173