Introduce FileWalker in ver. 1.77.2

So I’ve just recently disabled filewalker on startup on my nodes to try and avoid suspension strikes and node restarts as discussed in Fatal Error on my Node. This seems to have worked for me to stop the piecestore timeouts and node restarts. Is this change likely to have any impact in improving that? From what Alexey had said in that thread filewalker is really only necessary if the disk Storj uses is also used elsewhere, so in my case I’m not worried of having it disalbed. But I would prefer to run Storj as close to defaults as possible and would like to be able to re-enable filewalker on startup.