Intro. FindBugs' full :annotation (in addition to existing :jsr305)

Intro. FindBugs' full :annotation (in addition to existing :jsr305)

Having both of these is a required intermediate step, in order to switch
completely over to :annotation instead of :jsr305, which would be
preferable, because these two JARs define the same annotations and
overlap, which is never great.

This change will allow all downstream projects to gradually switch their
<dependency><groupId>com.google.code.findbugs from <artifactId>jsr305 to
<artifactId>annotations in all pom.xml. They will NOT have to adapt any
code, because the actual Java types are exactly the same (just from a
different Maven artefact).

When all downstream projects have switched over, then we'll replace what
this change added by the cleaner "real" solution prepared in
https://git.opendaylight.org/gerrit/#/c/47337/

see also discussion in https://git.opendaylight.org/gerrit/#/c/46914/

Change-Id: Ib026cd0338b263bb9663f2d1fa2a6cb167d6f136
Signed-off-by: Michael Vorburger <vorburger@redhat.com>