Remove missing terminals inspection object fields

[dnbln]

Fixes #20

[dnbln]

From what I can tell the UserDataHolderBase seems to be thread-safe, so maybe also change the ConcurrentLinkedQueues to plain ArrayList and the AtomicBooleans to plain Booleans?

[AzureMarker]

It looks like UserDataHolderBase is thread-safe in that setting a value is atomic, but performing a get and then modifying the value internally (such as using add on a list) is not inherently thread safe, so we need to keep the concurrent/atomic classes.