gnu: Add r-catterplots.

* gnu/packages/statistics.scm (r-catterplots): New variable.

gnu, doc: Use HTTPS for cran.r-project.org home pages.

* gnu/packages/bioinformatics.scm (r-sparql, r-acsnminer, r-gkmsvm)
(r-maldiquant, r-gprofiler)[home-page]: Use HTTPS.
* gnu/packages/cran.scm (r-colorspace, r-auc, r-calibrate, r-shape)
(r-compare, r-proxy, r-sp, r-rmtstat, r-lmtest, r-inline, r-bbmle)
(r-lpsolve, r-energy, r-suppdists, r-ksamples, r-cvst, r-drr, r-prodlim)
(r-ddalpha, r-rcpproll, r-ipred, r-psych, r-truncnorm, r-rsolnp, r-laeken)
(r-vcd, r-ica, r-scatterplot3d)[home-page]: Likewise.
* gnu/packages/machine-learning.scm (r-adaptivesparsity, r-kernlab)
[home-page]: Likewise.
* gnu/packages/maths.scm (r-quadprog, r-pracma)[home-page]: Likewise.
* gnu/packages/statistics.scm (r-boot, r-cluster, r-codetools, r-foreign)
(r-kernsmooth, r-nlme, r-mgcv, r-rpart, r-dichromat, r-estimability)
(r-pheatmap, r-labeling, r-magrittr, r-munsell, r-rcolorbrewer, r-sendmailr)
(r-gdtools, r-acepack, r-formula, r-locfit, r-chron, r-coda, r-backports)
(r-brew, r-commonmark, r-rstudioapi, r-plotrix, r-gridbase, r-bitops)
(r-catools, r-xnomial, r-lambda-r, r-whoreadsthis, r-futile-options)
(r-futile-logger, r-segmented, r-snow, r-iterators, r-foreach, r-doparallel)
(r-domc, r-irlba, r-registry, r-e1071, r-bigmemory-sri, r-r-methodss3)
(r-tidyselect, r-base64, r-runit, r-sfsmisc, r-gtools, r-gdata, r-gplots)
(r-ztable, r-vipor, r-sourcetools, r-statmod, r-compquadform, r-mixtools)
(r-fastica, r-diptest, r-modeltools, r-flexmix, r-deoptimr, r-pcapp)
(r-rrcov, r-fit-models, r-robust, r-trimcluster, r-fpc, r-fnn)
(r-modelmetrics, r-nloptr, r-lme4, r-tclust, r-lubridate)[home-page]:
Likewise.
* gnu/packages/web.scm (r-htmltools, r-hwriter, r-rjson, r-rook)[home-page]:
Likewise.
* doc/guix.texi (Invoking guix import, Invoking guix refresh): Likewise.

gnu: r-testthat: Update to 2.0.0.

* gnu/packages/statistics.scm (r-testthat): Update to 2.0.0.
[propagated-inputs]: Add r-cli, r-rlang, and r-withr.

gnu: r-ade4: Update to 1.7-10.

* gnu/packages/statistics.scm (r-ade4): Update to 1.7-10.
[propagated-inputs]: Add r-mass.

gnu: r-registry: Update to 0.5.

* gnu/packages/statistics.scm (r-registry): Update to 0.5.

gnu: r-iterators: Update to 1.0.9.

* gnu/packages/statistics.scm (r-iterators): Update to 1.0.9.

gnu: r-segmented: Update to 0.5-3.0.

* gnu/packages/statistics.scm (r-segmented): Update to 0.5-3.0.

gnu: r-rprojroot: Update to 1.3-1.

* gnu/packages/statistics.scm (r-rprojroot): Update to 1.3-1.

gnu: r-rcpparmadillo: Update to 0.8.300.1.0.

* gnu/packages/statistics.scm (r-rcpparmadillo): Update to 0.8.300.1.0.

gnu: r-plotrix: Update to 3.7.

* gnu/packages/statistics.scm (r-plotrix): Update to 3.7.

gnu: r-git2r: Update to 0.20.0.

* gnu/packages/statistics.scm (r-git2r): Update to 0.20.0.

gnu: r-backports: Update to 1.1.2.

* gnu/packages/statistics.scm (r-backports): Update to 1.1.2.

gnu: r-yaml: Update to 2.1.16.

* gnu/packages/statistics.scm (r-yaml): Update to 2.1.16.

gnu: r-reshape2: Update to 1.4.3.

* gnu/packages/statistics.scm (r-reshape2): Update to 1.4.3.

gnu: r-digest: Update to 0.6.13.

* gnu/packages/statistics.scm (r-digest): Update to 0.6.13.

gnu: Update r-cowplot to 0.9.2.

* gnu/packages/statistics.scm (r-cowplot): Update to 0.9.2.

gnu: r-foreach: Update to 1.4.4.

* gnu/packages/statistics.scm (r-foreach): Update to 1.4.4

gnu: r-caret: Update to 6.0-78.

* gnu/packages/statistics.scm (r-caret): Update to 6.0-78

gnu: r-domc: Update to 1.3.5.

* gnu/packages/statistics.scm (r-domc): Update to 1.3.5

gnu: Switch to using the version-major procedure.

* gnu/packages/audio.scm (ardour)[arguments]: Switch to using version-major.
  (hmmer)[source]: Switch to using version-major.
  (pidgin)[native-search-paths]: Switch to using version-major.
  (r-minimal)[source]: Switch to using version-major.