Add Utils.equalsIgnoreCase methods

This change also corrects usage of "frequency", "priority" and "score"
* Frequency is the relative probability in dictionary.
* Score is the relative probability in suggestions.
* Priority is kind a sorted score.

Change-Id: Iafb135a4ecdb401cc505014a07c74dfcac44d699
diff --git a/java/proguard.flags b/java/proguard.flags
index 729f4ad..914bd75 100644
--- a/java/proguard.flags
+++ b/java/proguard.flags
@@ -18,3 +18,7 @@
 -keep class com.android.inputmethod.latin.AutoCorrection {
   java.lang.CharSequence getAutoCorrectionWord();
 }
+
+-keep class com.android.inputmethod.latin.Utils {
+  boolean equalsIgnoreCase(...);
+}