aaa: renaming "authentication" to "aaa".

Renaming all places where "authentication" is used as package or module
name to "aaa" (Authentication, Authorization, accounting).

This is done as the "authentication" package/module deals not only with the
authentication part, but also with authorization part (via the Directory class
hierarchy)

Topic: AAA
Change-Id: Idd4410211deede8d17a4ce3a8ba1af32f0b497c5
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>