Improved performance a lot, changed settings UI a bit

app/src/main/java/de/kuschku/libquassel/QuasselClient.java

.../java/de/kuschku/libquassel/localtypes/BacklogFilter.java

...assel/localtypes/backlogstorage/HybridBacklogStorage.java

...e/kuschku/libquassel/syncables/types/impl/IrcChannel.java

...ku/libquassel/syncables/types/interfaces/QIrcChannel.java

...uschku/quasseldroid_ng/ui/chat/fragment/ChatFragment.java

...hku/quasseldroid_ng/ui/chat/nicklist/NickListAdapter.java

app/src/main/res/layout/activity_settings.xml