Simplify MetaDataBuffer - get rid of self-made prev/next pointers, use std::list if required

• The full-Seq window currently makes use of next(or prev?) to get the first meta of the next window: Instead, iterate on the MetaBuffer (We dont want to store a iterator to MetaBuffer in CircularWindowIterator)

• If we dont need prev/next interanlly, we can possibly even keep std::deque(instead of switching to std::list), and just remove the pointers