Implemented ability to use RxJava2 with LiveData

...java/de/kuschku/quasseldroid_ng/service/QuasselService.kt

...c/main/java/de/kuschku/quasseldroid_ng/ui/MainActivity.kt

...chku/quasseldroid_ng/util/helper/TransformationsHelper.kt

...main/java/de/kuschku/libquassel/session/CoreConnection.kt

...ain/java/de/kuschku/libquassel/session/ICoreConnection.kt

lib/src/main/java/de/kuschku/libquassel/session/Session.kt