Function uses caching - only the first usage scraps information from servers. Those
objects are then saved locally in temporary file and further usages loads needed data from the file.
Arguments bioc and local cannot be TRUE simultaneously.
If neither local nor bioc are TRUE, vector contains all packages available
currently on CRAN. If bioc is TRUE, vector contains all packages available currently
on CRAN and via Bioconductor. If local is TRUE, vactor contains all of the packages
that are currently installed.