Add operators to CompressedStorageIterator
Reference issue
What does this implement/fix?
Added all the comparison operators (couldn't hurt), += and -=. There are many operators required to satisfy RandomAccessIterator, and the vast majority appear to be satisfied. There are a few exceptions -- the iterator doesn't satisfy all the requirements of LegacyForwardIterator as it is not DefaultConstructible. Let me know if something else breaks your tests.