Add ocamlfind usage

[Drup]

It would be nice to have a --package flag to give a package. It would load the dependency recursively.

This is currently possible with ocp-browser --no-opamlib -I ocamlfind query -separator , -r PACKAGE``.
It's very useful for eliom, to avoid the module collision.

[rgrinberg]

Is it possible to reverse lookup a findlib package from a module? Would also be useful.

[Drup]

@rgrinberg No need to reverse lookup, ocp-index's engine posses the information (when loading the .cm*) it's just not propagated all the way down.

[AltGr]

I was a bit reluctant to add dependencies to findlib and META files, etc. but as long as we don't require them or findlib to be installed, I think it's fine. Adding a convenience shortcut for -I could indeed be useful.

@rgrinberg, we don't look at META files yet, so that would be difficult in the general case. However, you can get the location of the file that was used for lookup:

% ocp-index print LibIndex "%f"
/home/lg/.opam/4.02.3/lib/ocp-index/lib/libIndex.cmti

so looking up META files in the directory and its parents is definitely possible.