* Add selected chain store and optimize block locator with it
* Fix build error
* Fix comments
* Fix IsStaged
* Rename CalculateSelectedParentChainChanges to CalculateChainPath and SelectedParentChainChanges->SelectedChainPath
* Use binary.LittleEndian directly to allow compiler optimizations
* Remove boolean from HeadersSelectedChainStore interface
* Prevent endless loop in block locator
