Decouple Init Monitor and Storage from Init (a little bit)

It's been a while, that I started with this, so I hope I get everything together. The intention (as far as I remember) was to decouple the `Init`-object as much as possible from the `Monitor`- and especially the `Storage`- and `CachinInterface`-class(es). The later one doesn't need them anymore.

While I changed things I realized some interesting things, that took my attention: The tests.

* I assume, the `SessionCacheTest`-test never really worked, because at one point everyone failed. I realized, that it was missing `$_SESSION`, which isn't really suprising on CLI, but I wonder how it worked before.
* Some `FileCacheTest`-tests failed after I decoupled _annother_ test from `Init`. The only reason is, that this test relied on a change on the global `Init`-object made from the "other test".