Various lint error fixes.

> Fixing some RTL errors by specifying both marginStart and marginLeft
> Moving all layout direction checks to Utilities
> Explicitely adding @TargetApi before every method

Change-Id: Ibe9c52b93b5a6adeadb27ace2b312770fd732ea0
diff --git a/src/com/android/launcher3/Utilities.java b/src/com/android/launcher3/Utilities.java
index 2981747..f3435fc 100644
--- a/src/com/android/launcher3/Utilities.java
+++ b/src/com/android/launcher3/Utilities.java
@@ -631,4 +631,10 @@
         Matcher m = sTrimPattern.matcher(s);
         return m.replaceAll("$1");
     }
+
+    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
+    public static boolean isRtl(Resources res) {
+        return (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) &&
+                (res.getConfiguration().getLayoutDirection() == View.LAYOUT_DIRECTION_RTL);
+    }
 }