Removing make build files for sample apps.

There is no need to build these sample apps with make anymore.
Developers can simply use gradle.

This CL additionally adds gradle build config to SupportAppNavigation
app.

Test: None
Change-Id: Ia063e7b1dbd786f426a9d2abd074c8b1ad3d54b3
diff --git a/settings.gradle b/settings.gradle
index 34af0fe..89e8b10 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -144,6 +144,9 @@
 include ':support-animation-demos'
 project(':support-animation-demos').projectDir = new File(samplesRoot, 'SupportAnimationDemos')
 
+include ':support-app-navigation'
+project(':support-app-navigation').projectDir = new File(samplesRoot, 'SupportAppNavigation')
+
 /////////////////////////////
 //
 // External