added bigram prediction
  - after first character, only suggests bigram data (but doesn't autocomplete)
  - after second character, words from dictionary gets rearranged by using bigram
  - compatible with old dictionary
  - added preference option to disable bigram

Change-Id: Ia8f4e8fa55e797e86d858fd499887cd396388411
diff --git a/java/res/values/strings.xml b/java/res/values/strings.xml
index 35dd3e0..70a5b7e 100644
--- a/java/res/values/strings.xml
+++ b/java/res/values/strings.xml
@@ -85,6 +85,11 @@
     <!-- Description for auto completion -->
     <string name="auto_complete_summary">Spacebar and punctuation automatically insert highlighted word</string>
     
+    <!-- Option to enable bigram completion -->
+    <string name="bigram_suggestion">Bigram Suggestions</string>
+    <!-- Description for auto completion -->
+    <string name="bigram_suggestion_summary">Use previous word to improve suggestion</string>
+
     <!-- Array of prediction modes -->
     <string-array name="prediction_modes">
         <item>None</item>
diff --git a/java/res/xml/prefs.xml b/java/res/xml/prefs.xml
index 535b63f..c93fe0a 100644
--- a/java/res/xml/prefs.xml
+++ b/java/res/xml/prefs.xml
@@ -81,6 +81,14 @@
             android:defaultValue="@bool/enable_autocorrect"
             android:dependency="show_suggestions"
             />
-            
+
+        <CheckBoxPreference
+            android:key="bigram_suggestion"
+            android:title="@string/bigram_suggestion"
+            android:summary="@string/bigram_suggestion_summary"
+            android:persistent="true"
+            android:defaultValue="true"
+            android:dependency="auto_complete"
+            />
     </PreferenceCategory>            
 </PreferenceScreen>