Create lifecycle:livedata-core dependency

Move the core classes of LiveData into a separate
lifecycle:livedata-core dependency that represents
the very minimal API surface needed for LiveData.

The lifecycle:livedata dependency will keep the
non-essential LiveData APIs (such as Transformations
and MediatorLiveData) and have livedata-core as a
transitive dependency.

Test: tests still pass
BUG: 70681466
Change-Id: I1d2974f7f95f27e19bcca8be32d0ddc4283d5d43
diff --git a/lifecycle/livedata-core/src/main/AndroidManifest.xml b/lifecycle/livedata-core/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..6d2f964
--- /dev/null
+++ b/lifecycle/livedata-core/src/main/AndroidManifest.xml
@@ -0,0 +1,19 @@
+<!--
+  ~ Copyright 2017 The Android Open Source Project
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~      http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="android.arch.lifecycle.livedata.core">
+</manifest>