[libnozzle] rename libtap to libnozzle (part 1)

Our fearless Debian maintainer wferi made us aware that TAP is an overloaded
term already and it would be very confusing to add yet another one.

nozzle is a good pick from http://www.thesaurus.com/browse/tap

I am sure lib*cock* would have cause havoc :-)

This commit only rename files and allow builds. The API needs to be renamed too,
but that will come over time with major code cleanup as documented here:
https://trello.com/c/pyEKd4UH/396-libnozzle-make-it-production-ga-ready

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>