libpipeline: Add package

[Bjørn Forsman: modify meta.description so that it doesn't include the
package name and doesn't end in a period.]
man-db: Upgrade package from 2.5.1 -> 2.6.6

Additionally, remove the uneeded share.patch since share/man is now
searched within upstream code.
fish: Fix propagatedBuildInputs and other assorted changes

Currently, fish does not depend on python27 which is necessary for many
of the built in commands such as the manpage completion generator and
the web configuration sevice. This patch adds support for python27 as
well as man_db for the manpage completion generator. It also attempts to
replace more shell functions with binaries contained in the nix store.