Introduces rounded square avatars, properly colors avatars

...uschku/quasseldroid/service/QuasselNotificationBackend.kt

...kuschku/quasseldroid/ui/chat/buffers/BufferListAdapter.kt

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

...kuschku/quasseldroid/ui/chat/input/AutoCompleteAdapter.kt

.../kuschku/quasseldroid/ui/chat/input/AutoCompleteHelper.kt

...u/quasseldroid/ui/chat/messages/QuasselMessageRenderer.kt

...de/kuschku/quasseldroid/ui/chat/nicks/NickListFragment.kt

...n/java/de/kuschku/quasseldroid/util/helper/GlideHelper.kt

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

...e/kuschku/quasseldroid/viewmodel/data/AutoCompleteItem.kt