GSoC 2018 - boot sector finished

Hi all!

Sorry, haven’t written anything for a while. Let me tell you what have been done since last post.

BTRFS boot sector

TL;DR: It works!

Boot sector works!

I’ve been able to load main bootloader code from freeldr.sys into memory, transfer control to it and get on error message (freeldr.sys can’t find its config file - I haven’t written second-stage BTRFS code yet).