Simplified and refactored the PageCache class. Made it throw exceptions rather than have a state based error system.
Made it a DisposableObject and correctly disposed the NativeAlignedBuffer
Cleaned up the PhiSentenceFormat definition?
Made a TERRIBLE test for the PageCache class that clearly demonstrates why it's not thread safe.

Created the AsyncOp class as an experiment for encapsulating cancelable, reporting asynchronous tasks. It might be better to have this be an abstract base class, rather than an instance-based class due to the inflexability of the delegate system.