Ability for released binaries to *not* augment findlib path.

[jordwalke]

We still want to export a wrapper script that execs the correct version of the binary, but without augmenting things like OCAMLPATH - or really any part of the environment.

Here's a couple of examples where it's important:

# The  local project's `esy` environment is overwritten by the `esyvim`
# binary wrapper's environment.
esy esyvim myFile.re

# If vim is using the globally installed `ocamlmerlin` that has a wrapper
# then the local project's `esy` environment will be overwritten by
# the global `ocamlmerlin`'s. This forces you to install merlin as a dev
# dependency which is also a good approach, but it would be nice if
# you didn't have to.  
esy vim myFile.re

This can really only be decided on a per application basis. Packages that are released must decide if it makes sense for their use case to wrap the binaries.

I'd say that esyvim would opt out of wrapping, and so would ocamlmerlin.

The other approach is to let released binaries decide if they want to wrap, but only if not already running in an environment.