Start enforcing javac warnings.

- Add new ways to ignore warnings for modules with warnings
- Enable -Xlint:deprecation and -Xlint:unchecked by default to
  prevent regressions.

Test: ./gradlew assembleDebug
Change-Id: I95f73afde042a2d61984f59ee3d3350a013c0044
diff --git a/wear/build.gradle b/wear/build.gradle
index c70ebef..0f606f1 100644
--- a/wear/build.gradle
+++ b/wear/build.gradle
@@ -42,4 +42,5 @@
     inceptionYear = "2016"
     description = "Android Wear Support UI"
     minSdkVersion = 23
+    failOnDeprecationWarnings = false
 }