Move Litho Flipper Plugin to Litho

Summary:
The current ownership and release model prevents cleanly releasing new versions of the plugin while the code is split between two repos.

This diff moves the flipper-litho plugin to the Litho repository. You'll find new releases as `litho-editor-flipper` that'll be reexported via gradle's `api` to the old artifact.

Reviewed By: colriot

Differential Revision: D23962234

fbshipit-source-id: 7884423342904219ae9b41632c6df90cda870798

android/plugins/litho/build.gradle

@@ -21,8 +21,8 @@ android {
         compileOnly deps.lithoAnnotations
         implementation project(':android')
         implementation deps.lithoCore
-        implementation deps.lithoEditorCore
-        implementation(deps.lithoEditorFlipper) {
+        api deps.lithoEditorCore
+        api(deps.lithoEditorFlipper) {
             exclude group:'com.facebook.flipper', module:'flipper'
         }
         implementation deps.lithoSectionsDebug