Move Partner.java into the Wallpaper directory.

WallpaperPicker depends on this and have this class in Launcher3 would cause a
circular dependency in google3

Change-Id: Ia582bcb988a4f6375904660546b1bc1744d25238
diff --git a/src/com/android/launcher3/Partner.java b/WallpaperPicker/src/com/android/launcher3/Partner.java
similarity index 100%
rename from src/com/android/launcher3/Partner.java
rename to WallpaperPicker/src/com/android/launcher3/Partner.java