This PR does minor code improvements, as follows:

• Container.java: Use a ConcurrentHashMap in the static cache, to ensure thread safty like Marshalling.TYPE_CACHE does.
• Marshalling.java, DBusDaemon.java, DirectConnection.java: Avoid creating empty arrays disposed after passing it to toArray.
• PrimitiveUtils.java: _clz1 == _clz2 does match in line 74, the removed code is therefore not reachable
• RemoteInvocationHandler.java: use switch (String) instead of if/else if