Delete Sessions which cause deserialization errors

Trying to deserialize sessions that are for some reason not
deserializable leads to continous retries at the moment.

As the data is apparently not loadable, it might be a better idea
to remove the data from memcached alltogether in order to avoid
expensive retries.
Merge branch 'auto_delete' of github.com:marcust/memcached-session-manager into marcust-auto_delete

Conflicts:
	kryo-serializer/src/main/java/de/javakaffee/web/msm/serializer/kryo/KryoTranscoderFactory.java
Let all serializers throw TranscoderDeserializationException on deser errors.