Added default non-null behavior

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Removed integration section for everything except Maven

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Updated license informations

Signed-off-by: Sebastian Hoß <mail@shoss.de>
FindBugs regressions marked

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Nullsafe-operations

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Replaced strings with constants

Signed-off-by: Sebastian Hoß <mail@shoss.de>
Split units-implementation into submodules

Signed-off-by: Sebastian Hoß <mail@shoss.de>