Add aliases.rds, rdxrefs.rds, and html manuals to the postrun step

[jwokaty]

Incorporate code from Bioconductor/biocViews#15 to generate aliases.rds, rdxrefs.rds, and html manuals. The best time to do this seems to be the postrun on the primary builder. The new biocViews functions work on package sources. We should generate these files for packages that will be or were previously propagated.

• aliases.rds and rdxrefs.rds should be placed in the reposRoot/src/contrib/Meta path, like https://cran.r-project.org/src/contrib/Meta/.
• The files could be generated via an R script that's wrapped in a Python script and is called after making PROPAGATION_STATUS_DB following https://github.com/Bioconductor/BBS/blob/devel/BBS-make-PROPAGATION_STATUS_DB.py as an example.
• html manuals will be placed in the same directory as their PDF counterparts.
• manuals should be created for software, annotations*, and experiments*.