Fixed bugs regarding buffer loading and init

...main/java/de/kuschku/libquassel/client/BufferManager.java

app/src/main/java/de/kuschku/libquassel/client/Client.java

.../libquassel/localtypes/backlogstorage/BacklogStorage.java

...assel/localtypes/backlogstorage/MemoryBacklogStorage.java

...u/libquassel/syncables/types/abstracts/ABufferSyncer.java

...schku/libquassel/syncables/types/impl/BacklogManager.java

...kuschku/libquassel/syncables/types/impl/BufferSyncer.java

...hku/libquassel/syncables/types/impl/BufferViewConfig.java

...ibquassel/syncables/types/interfaces/QBacklogManager.java

.../libquassel/syncables/types/interfaces/QBufferSyncer.java

...java/de/kuschku/quasseldroid_ng/ui/chat/ChatActivity.java

...de/kuschku/quasseldroid_ng/ui/chat/drawer/BufferItem.java

.../quasseldroid_ng/ui/chat/drawer/BufferViewConfigItem.java