Added preference to manage repositories

As this is no longer a top level menu item, it is now the first item
in the settings, under "Updates".

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

@@ -109,6 +109,7 @@
 
     <string name="menu_update_repo">Update Repos</string>
     <string name="menu_manage">Repositories</string>
+    <string name="repositories_summary">Add additional sources of applications</string>
     <string name="menu_send_apk_bt">Share F-Droid by Bluetooth</string>
     <string name="menu_settings">Settings</string>
     <string name="menu_about">About</string>

app/src/main/res/xml/preferences.xml

@@ -1,6 +1,14 @@
 <?xml version="1.0" encoding="utf-8"?>
 <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
     <PreferenceCategory android:title="@string/updates">
+        <PreferenceScreen
+            android:title="@string/menu_manage"
+            android:summary="@string/repositories_summary">
+            <intent
+                android:action="android.intent.action.MAIN"
+                android:targetPackage="org.fdroid.fdroid"
+                android:targetClass="org.fdroid.fdroid.views.ManageReposActivity" />
+        </PreferenceScreen>
         <com.geecko.QuickLyric.view.AppCompatListPreference android:title="@string/update_interval"
             android:key="updateInterval"
             android:defaultValue="24"