Support project-wide prune (account prune with option)

[HyperBrain]

When working with different people/teams in an AWS account it is not very helpful to have account wide pruning only.

Imagine some developers doing experiments on a test project (where lots of old test lambdas can remain) a project wide pruning would be very helpful.

The prune plugin should only prune functions contained in the active project by default, but when started with --all or --account prune everything everywhere.

[jasich]

@HyperBrain I think I'm in agreement with what you're saying. It looks like the plugin prunes every lambda it can find. It looked like it was pruning lambda functions that weren't even in the project I was running it in. You're saying that it should be scoped to only the current project and have a separate flag that causes it to prune everything every where right? If so, Yeah 💯