Additional changes:
- Fix demo that was broken in `a27fa92f8fe6f16cb301680de7202d68983f94dc`. `frameworks` in podspec was replaced with `OTHER_LDFLAGS`, because frameworks propagate to target for no good reason. `OTHER_LDFLAGS` is probably necessary, because of mixed-langage frameworks that break "auto linking".
- Update `UIDevice+Extension.swift` to get new device names in test error messages.
- Fix long installation of pods in Demo by caching `get_mixbox_version` (it was executed numerous amount of times, and now it's called once).
- CI code was simplified, some code was shared, some outdated kludges were removed.