- Add inbound and outbound group sessions

.../src/main/java/org/matrix/olm/OlmInboundGroupSession.java

...src/main/java/org/matrix/olm/OlmOutboundGroupSession.java

...m-sdk/src/main/java/org/matrix/olm/OlmUtilsException.java

java/android/OlmLibSdk/olm-sdk/src/main/jni/Android.mk

java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_account.cpp

...LibSdk/olm-sdk/src/main/jni/olm_inbound_group_session.cpp

java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_jni.h

...android/OlmLibSdk/olm-sdk/src/main/jni/olm_jni_helper.cpp

...ibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.cpp

...mLibSdk/olm-sdk/src/main/jni/olm_outbound_group_session.h

java/android/OlmLibSdk/olm-sdk/src/main/jni/olm_session.cpp