pkg/lib: fix `pkg-catalog-update-local` version selection

Also fixes problems with using a relative target path
with `raco pkg catalog-archive`.
raco pkg catalog-archive: parse sources like `catalog-copy`
raco pkg catalog-show: improve output format

Separate packages with a blank line, and fix formatting of
a module list.
raco pkg catalog-archive: keep module & dependency info

Also fixes another relative-path problem.
update RacketCon page to add the group-rate reservation link

Plus various adjustments to the format.
pkg/db: make local package database's path relative to installation name

Instead of `(version)`, use `(get-installation-name)` for the path
of the local database used by the GUI package manager.