Migrations framework

[AuHau]

There are slowly creeping migration changes into Desktop, which are required either from Bee's changes or internal changes. So far, they have been in the form of "change name" which is easy to be detected and applied, but in the future, this could grow into more complex migrations. I would therefore propose similar system that IPFS uses (go's migration tool and js's migration tool that I have originally wrote). The basic concept would be to version the "store" and have migrations that move the "store" from one version to another.