guix: Add archive support for bioconductor-uri.

* guix/build-system/r.scm (bioconductor-uri): Also return the archive URL.
* guix/import/cran.scm (latest-bioconductor-release, fetch-description):
Adjust because bioconductor-uri now returns a list.

import: cran: Use Bioconductor 3.6 helpers.

* guix/import/cran.scm (bioconductor-mirror-url): Remove procedure.
(fetch-description): Extract DESCRIPTION file from tarball for Bioconductor
packages.
(latest-bioconductor-release): Use latest-bioconductor-package-version.

import: cran: Add support for Bioconductor 3.6.

* guix/import/cran.scm (%bioconductor-version,
%bioconductor-packages-list-url): New variables.
(bioconductor-packages-list, latest-bioconductor-package-version): New
procedures.

import: utils: Add string helpers.

* guix/import/utils.scm (read-lines, chunk-lines): New procedures.

Revert "import: cpan: Use HTTPS for home pages."

This reverts commit 29f7bf59d5d4d4b848eaedc6766bb4e02cae20d3: HTTPS support
at search.cpan.org is unreliable, at best.  Don't rely on it.

import: cpan: Use HTTPS for home pages.

* guix/import/cpan.scm (cpan-home): Use HTTPS.
* tests/cpan.scm ("cpan->guix-package"): Expect it.

import: cpan: Actually use CPAN-HOME.

* guix/import/cpan.scm (cpan-module->sexp): Use the CPAN-HOME procedure.

import: cpan: Add trailing "/" to CPAN-HOME.

Prevent regression after commit e4bc1727302b0e1e255ea5cf4e2ccf33cafe7296.

* guix/import/cpan.scm (cpan-home): Add trailing "/".

import: cpan: Add trailing "/" on home-page.

This appeases 'guix lint', which otherwise complains about permanent
redirects.

* guix/import/cpan.scm (cpan-module->sexp): Add trailing "/" on home-page.
* tests/cpan.scm ("cpan->guix-package"): Adjust accordingly.

import: cpan: Propagate imported dependencies.

This is most often the need for perl module dependencies.

* guix/import/cpan.scm (cpan-module->sexp): 'inputs -> 'propagated-inputs.
* tests/cpan.scm ("cpan->guix-package"): Adjust accordingly.

import: elpa: Do not abort when failing to download the archive.

* guix/import/elpa.scm (elpa-fetch-archive): Use 'http-fetch/cached'
directly instead of 'call-with-downloaded-file'.  This ensures we don't
just abort when networking access is lacking, which is required to allow
'guix refresh -c refresh' to proceed.

import: github: Gracefully handle multiple-URL origins.

* guix/import/github.scm (latest-release)[origin-github-uri]: New
procedure.  Use it.

Use HTTPS for bioconductor.org.

* doc/guix.texi (Invoking guix import, Invoking guix refresh): Use HTTPS for
bioconductor.org URLs.
* gnu/packages/bioinformatics.scm (r-annotate, r-geneplotter, r-genefilter)
(r-deseq2, r-dexseq, r-annotationforge, r-rbgl, r-gseabase, r-category)
(r-gostats, r-shortread, r-biocgenerics, r-biocinstaller, r-biocviews)
(r-biocstyle, r-bioccheck, r-s4vectors, r-iranges, r-genomeinfodbdata)
(r-genomeinfodb, r-xvector, r-genomicranges, r-biobase, r-annotationdbi)
(r-biomart, r-biocparallel, r-biostrings, r-rsamtools, r-delayedarray)
(r-summarizedexperiment, r-genomicalignments, r-rtracklayer)
(r-genomicfeatures, r-graph, r-topgo, r-bsgenome, r-impute, r-seqpattern)
(r-seqlogo, r-motifrg, r-bamsignals, r-mutationalpatterns, r-tximport)
(r-rhdf5, r-chipseq, r-sva, r-affy, r-vsn, r-mzid, r-msnid)
(r-interactivedisplaybase, r-annotationhub)[home-page]: Likewise.
* gnu/packages/bioinformatics.scm (r-txdb-hsapiens-ucsc-hg19-knowngene)
(r-go-db, r-bsgenome-hsapiens-1000genomes-hs37d5, r-org-hs-eg-db)
(r-org-ce-eg-db, r-org-dm-eg-db, r-org-mm-eg-db)
(r-bsgenome-hsapiens-ucsc-hg19, r-bsgenome-mmusculus-ucsc-mm9)
(r-bsgenome-mmusculus-ucsc-mm10, r-txdb-mmusculus-ucsc-mm10-knowngene)
(r-bsgenome-celegans-ucsc-ce6, r-bsgenome-celegans-ucsc-ce10)
(r-bsgenome-dmelanogaster-ucsc-dm3, r-copyhelper)[source, home-page]:
Likewise.
* gnu/packages/statistics.scm (r-rcurl)[source]: Likewise.
* guix/build-system/r.scm (bioconductor-uri): Likewise.
* guix/import/cran.scm (%cran-url, bioconductor-package?)
(bioconductor-data-package?, bioconductor-experiment-package?): Likewise.

import: cpan: Load (gnu packages perl) lazily.

* guix/import/cpan.scm: Remove dependency on (gnu packages perl).
(perl-package): New procedure.
(%corelist, core-module?): Use it instead of referring to 'perl'.

import: pypi: Remove unneeded import.

* guix/import/pypi.scm: Remove unneeded import.

Merge branch 'master' into staging

import: Add generic data to package converter.

* guix/import/utils.scm (build-system-modules, lookup-build-system-by-name,
specs->package-lists, source-spec->object, alist->package): New procedures.
* tests/import-utils.scm: Add tests for alist->package.

import: Add package->code.

* guix/import/print.scm: New file.
* tests/print.scm: New file.
* Makefile.am (SCM_TESTS): Add new test file.
(MODULES): Add print.scm.

Merge branch 'master' into staging

upstream: Add new GNOME updater.

Partly fixes <https://bugs.gnu.org/28159>.
Reported by Hartmut Goebel <h.goebel@crazy-compilers.com>.

* guix/import/gnome.scm: New file.
* Makefile.am (MODULES): Add it.
* guix/gnu-maintenance.scm (latest-gnome-release)
(%gnome-updater): Remove.