Allow multiple directories to be chowned, and allow disabling recursive chowning

[FooBarWidget]

Right now we chown the home dir, which may be slow if there are many files in the home dir. During dogfooding we've already seen cases in which the home directory can end up with many files:

• User mounts a volume into the home dir: solvable by not crossing filesystem boundaries.
• rust-musl-builder uses rustup to install Rust into ~/.rustup.
• In our own images we use Bundler to install a bundle to ~/bundle.

We've dealed with the latter two issues by turning off home dir chown completely, and to introduce a hook which only chowns ~/* non-recursively, but this is a pain. We should make the chown system more configurable.

We should allow chowning an arbitrary number of globs. For each glob, the user should be able to specify whether to chown that recursively.