Remove meta pointers

This should cover what you described in !7 (comment 52164).

Addresses #50 (closed)

Existing tests are passing. I only had to update the one that used meta pointers directly.

For FULL_SEQ the State is used in full and I believe properly handled. However for Streaming and Triggered the state is not used in any meaningful way. Should it be?

One more thing I noticed is that as far as I can see streaming is calling updateMetaWindowAccordingToSampleWindow twice, once in the actual updateStreamingWindowIter and then again in the DataReadyHandlerStreaming::moveWindows. If I remove either one of the calls the tests still pass, while removing both makes the tests fail, so maybe one of them is redundant.