Health API: Provide means to resolve conflicting result `Fix`es

With the merge of https://github.com/cryptomator/cryptofs/pull/149, a result returns an `Fix` object, which represents the fix for the result (meaning that after applying the fix, the result does not appear again in a subsequent check).

Still, a key problem is not fixed: **How to resolve conflicting (aka affecting the same resource) fixes?**

It is explicitly spoken of _fixes_ not only results, because a fix can affect more paths than just the result-causing ones. Example
> Result A reports a file at the wrong place `/Foo/Bar.c9r`. The Fix is to move it to `/Baz/Bar.c9r`.
The result-causing paths are only `/Foo/Bar.c9r`, but the fix-affected paths are `/Foo/Bar.c9r` and `/Baz/Bar.c9r`.

Every fix alters the state of the filesystem, hence, subsequent fixes (including the same fix) might fail. Currently, the health API does not account for that and only _reports_ all problems of the current filesystem state. The consumer can only execute one fix after another and rerun the health check(s) to fix previously failed fixes.