Add MangaDex only implementation of Mangadex Follows list

Add login dialog that pops up whenever you are not logged in when trying to browse MangaDex
Remove attempts at porting over chapter read history from older galleries to new ones
Disable latest for ExHentai, it was browse without buttons anyway

app/src/main/java/exh/source/EnhancedHttpSource.kt

@@ -1,6 +1,7 @@
 package exh.source
 
 import eu.kanade.tachiyomi.data.preference.PreferencesHelper
+import eu.kanade.tachiyomi.source.Source
 import eu.kanade.tachiyomi.source.model.FilterList
 import eu.kanade.tachiyomi.source.model.MangasPage
 import eu.kanade.tachiyomi.source.model.Page
@@ -234,4 +235,21 @@ class EnhancedHttpSource(
             originalSource
         }
     }
+
+    companion object {
+        fun Source.getMainSource(): Source {
+            return if (this is EnhancedHttpSource) {
+                this.source()
+            } else {
+                this
+            }
+        }
+        fun Source.getOriginalSource(): Source {
+            return if (this is EnhancedHttpSource) {
+                this.originalSource
+            } else {
+                this
+            }
+        }
+    }
 }