Factor out functions over OPAM universes and the command line query interface

Now in ocamllabs/opamfu
Use new repository namespace polymorphic variant symbols
Render dependency formula with structure and hyperlinks. Fixes #41
Sort alphanumerically ignoring case (the same way that opam does it)
Add constrained reverse and optional reverse dependency rendering. Fixes #78.
like a rolling stone
Use publication date terminology
Show OCaml compiler constraint on package page. Closes #70.
Add uri and js_of_ocaml deps to README
Fix edit link relative resolution bug. Fixes ocaml/ocaml.org#356
Really align the path structure to an opam repository (pkg/ -> packages/)
Merge pull request #81 from dsheets/opamfu

Factor out functions over OPAM universes and the command line query interface