findbugs: adding category ignore list

Added a new list in exclude-filters-general.xml.
This list represent categories that we decided not to fix for now or
categories that we do want to attend in the future (mark as TBD)

when running:
$ mvn findbugs:findbugs
will filter the project specific bugs which choose to ignore

when running:
$ mvn findbugs:findbugs -P findbugs-general
will filter project specific as well as the general category list

Change-Id: Idfbc37df07eff4c212cc5210965cabd79a51df36
Signed-off-by: Shahar Havivi <shavivi@redhat.com>