Bug fixes & code improvements

- simplified access to MainActivity
- fixed bug where the 'unread' tag wasn't updated
- aboutlibraries version bump

app/build.gradle

@@ -79,7 +79,7 @@ dependencies {
     implementation('com.mikepenz:materialdrawer:6.0.2@aar') {
         transitive = true
     }
-    implementation('com.mikepenz:aboutlibraries:6.0.1@aar') {
+    implementation('com.mikepenz:aboutlibraries:6.0.2@aar') {
         transitive = true
     }
     implementation "com.mikepenz:iconics-core:3.0.0@aar"