Introduce particle states

Add the particle MC states (see km3net-dataformat#42) in KM3BUU.

km3buu/tests/test_output.py

@@ -98,6 +98,7 @@ class TestAANET(unittest.TestCase):
         evt = self.fobj.events[0]
         np.testing.assert_array_equal(evt.mc_tracks.pdgid,
                                       [12, 2212, 111, 211, -211])
+        np.testing.assert_array_equal(evt.mc_tracks.status, [0, 1, 1, 1, 1])
         np.testing.assert_array_almost_equal(
             evt.mc_tracks.E,
             [11.90433897, 1.45689677, 0.49284856, 8.33975778, 0.28362369])