use 'phone' or 'tablet' as default resource

src/main/java/eu/siacs/conversations/services/XmppConnectionService.java

@@ -851,7 +851,7 @@ public class XmppConnectionService extends Service implements OnPhoneContactsLoa
 
 	public XmppConnection createConnection(final Account account) {
 		final SharedPreferences sharedPref = getPreferences();
-		account.setResource(sharedPref.getString("resource", "mobile")
+		account.setResource(sharedPref.getString("resource", getString(R.string.default_resource))
 				.toLowerCase(Locale.getDefault()));
 		final XmppConnection connection = new XmppConnection(account, this);
 		connection.setOnMessagePacketReceivedListener(this.mMessageParser);

src/main/res/values-sw600dp/defaults.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="default_resource">Tablet</string>
+</resources>

src/main/res/values/defaults.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="default_resource">Phone</string>
+</resources>

src/main/res/xml/preferences.xml

@@ -9,7 +9,7 @@
             android:title="@string/pref_grant_presence_updates"/>
 
         <ListPreference
-            android:defaultValue="Mobile"
+            android:defaultValue="@string/default_resource"
             android:entries="@array/resources"
             android:entryValues="@array/resources"
             android:key="resource"