Fixed Lint issues

app/build.gradle.kts

.../kuschku/quasseldroid_ng/persistence/PersistentSession.kt

...de/kuschku/quasseldroid_ng/persistence/QuasselDatabase.kt

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

...schku/quasseldroid_ng/ui/setup/accounts/AccountAdapter.kt

...uasseldroid_ng/ui/setup/accounts/AccountSelectionSlide.kt

...src/main/java/de/kuschku/quasseldroid_ng/util/Patterns.kt

.../de/kuschku/quasseldroid_ng/util/helper/LiveDataHelper.kt

...e/kuschku/quasseldroid_ng/util/helper/ObservableHelper.kt

...ku/quasseldroid_ng/util/helper/SharedPreferencesHelper.kt

app/src/main/res/layout-sw600dp-land/activity_setup.xml

app/src/main/res/layout-sw600dp-land/setup_slide.xml

app/src/main/res/layout-sw600dp/activity_setup.xml

app/src/main/res/layout-sw600dp/setup_slide.xml

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

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

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

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

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

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