List missing features on connect. Fixes #53

app/sampledata/features.json

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

...a/de/kuschku/quasseldroid/util/ui/ColorChooserDialog.java

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

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

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