Depict opam update

[Jerry James]

I just checked in a big update to the opam front end for depict
(https://pagure.io/depict).  It now handles complex boolean
dependencies much better.  Try this to see a dependency graph for
Facebook's Infer, assuming you have a git checkout of opam-repository
at ~/src/opam-repository:

python3 -m depict --input=json examples/opam.js --input=opam --exclude
mirage-xen:mirage-xen-ocaml:ocamlfind-secondary --stop ocaml
--repository ~/src/opam-repository async ANSITerminal apron atdgen
base64 cmdliner core conf-autoconf conf-gmp conf-mpfr conf-sqlite3
conf-zlib ctypes dune elina javalib mlgmpidl mtime ocamlfind
ocamlgraph ounit parmap ppx_deriving ppx_fields_conv ppx_let sawja
sqlite3 utop xmlm yojson zarith --graph=dag --output=dot infer.dot
--output=layered -