Improve reactivity, add nicklist button

...main/java/de/kuschku/quasseldroid/ui/chat/ChatActivity.kt

...u/quasseldroid/ui/chat/buffers/BufferViewConfigAdapter.kt

.../quasseldroid/ui/chat/buffers/BufferViewConfigFragment.kt

app/src/main/res/drawable/ic_account_multiple.xml

app/src/main/res/menu/activity_main.xml

app/src/main/res/values-de/strings.xml

app/src/main/res/values/strings.xml