JNITranslator: no session provided? create one on the fly.
JNITranslator: no session provided? create one on the fly.

Fixes global translations without a session -- these were keeping their cache, which also means
changing context or feature weights did not have the desired effect for these translations.

Fixes regression in 661ea5d05d40bc88b5eee76f608818cedf199309, fixes #127, hopefully for good.

letconex/MMT,ModernMT/MMT,ModernMT/MMT,letconex/MMT,letconex/MMT,letconex/MMT,ModernMT/MMT,letconex/MMT,letconex/MMT,ModernMT/MMT,ModernMT/MMT