Tidy up styling and tinting in NavigationView

Currently there is no way to set a different tint/color
for the text and icon. This icon splits them up and tidies
up some of the internal state.

Change-Id: I5d81f19dddf2df6cfc983fc2a60b2353a780d522
diff --git a/design/api/current.txt b/design/api/current.txt
index 94e0f9c..e7c86a0 100644
--- a/design/api/current.txt
+++ b/design/api/current.txt
@@ -156,14 +156,17 @@
     ctor public NavigationView(android.content.Context, android.util.AttributeSet);
     ctor public NavigationView(android.content.Context, android.util.AttributeSet, int);
     method public void addHeaderView(android.view.View);
-    method public int getItemBackgroundResource();
-    method public android.content.res.ColorStateList getItemTintList();
+    method public android.graphics.drawable.Drawable getItemBackground();
+    method public android.content.res.ColorStateList getItemIconTintList();
+    method public android.content.res.ColorStateList getItemTextColor();
     method public android.view.Menu getMenu();
     method public android.view.View inflateHeaderView(int);
     method public void inflateMenu(int);
     method public void removeHeaderView(android.view.View);
+    method public void setItemBackground(android.graphics.drawable.Drawable);
     method public void setItemBackgroundResource(int);
-    method public void setItemTintList(android.content.res.ColorStateList);
+    method public void setItemIconTintList(android.content.res.ColorStateList);
+    method public void setItemTextColor(android.content.res.ColorStateList);
     method public void setNavigationItemSelectedListener(android.support.design.widget.NavigationView.OnNavigationItemSelectedListener);
   }