Bump configuration version to 8 with a webinterface-removal notice

The webinterface fields are gone from the Configuration class so any
existing entries (WebinterfacePassword, AuthStore, WebinterfacePort
and friends) get dropped on the next save automatically — Newtonsoft
silently skips properties the target type does not declare. The
version bump itself is what stops the one-shot notification from
firing on every launch.

A new pair of HellionStrings entries (EN + DE) explains the change to
users coming from 0.1.x. Title: "Hellion Chat 0.2.0", body points at
the README for context. Notification fires once per upgrade.

ChatTwo/Configuration.cs

@@ -33,7 +33,7 @@ public class ConfigKeyBind
 [Serializable]
 public class Configuration : IPluginConfiguration
 {
-    private const int LatestVersion = 7;
+    private const int LatestVersion = 8;
 
     public int Version { get; set; } = LatestVersion;