various tweaks & fixes

Mostly for
https://github.com/libgdx/libgdx/issues/2359
https://github.com/libgdx/libgdx/issues/2524
https://github.com/libgdx/libgdx/issues/2441
https://github.com/libgdx/libgdx/issues/2436

Yes, I'm aware of that, that's why I called `containsValue( value, identity = false );` and so on... Did I miss that parameter somewhere or is there something else wrong with it?