Clarify the story on building/running/installing tests and doc · ocaml/opam@4170148- `build-test:`, `build-doc:` are deprecated - they should be integrated into `build:` and `install:`, with filters based on the new variables `with-test`, `with-doc` - variables `test` and `doc` available in the `depends:`, `depopts:` fields renamed to `with-test`, `with-doc` for consistency - likewise, command-line options `--build-test` renamed to `--with-test`, etc. - `run-test:` is also avail
opam - OPAM 1.2 and Travis CI
