Make fresco a stand-alone gradle project (#548)

Summary:
Pull Request resolved: https://github.com/facebook/flipper/pull/548

First project to pull out of the "fat distribution" we currently have.
Still needs setup for Maven and registration in Bintray.

Reviewed By: jknoxville

Differential Revision: D17395660

fbshipit-source-id: 6244495a2e25d705dd930ef87c7e5e1f038eb921

android/sample/build.gradle

@@ -67,5 +67,6 @@ dependencies {
     testImplementation deps.junit
 
     debugImplementation project(':android')
+    debugImplementation project(':fresco-plugin')
     releaseImplementation project(':noop')
 }