Centralize version and target sdk constants

We had these specified directly in AndroidManifest.xml due to
our internal build setup. This change makes our internal build
re-write AndroidManifest.xml to dynamically insert the required
values, meaning they no longer need specifying in each manifest.

Bonus 1: Internally built demo apps now include the CL number at
which they're built in the version name :).

Bonus 2: Removes lint warning that complains min/target SDK
values in the manifest are redundant.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188489115

constants.gradle

@@ -12,13 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 project.ext {
+    // ExoPlayer version and version code.
+    releaseVersion = '2.7.0'
+    releaseVersionCode = 2700
     // Important: ExoPlayer specifies a minSdkVersion of 14 because various
     // components provided by the library may be of use on older devices.
     // However, please note that the core media playback functionality provided
     // by the library requires API level 16 or greater.
     minSdkVersion = 14
-    compileSdkVersion = 27
     targetSdkVersion = 27
+    compileSdkVersion = 27
     buildToolsVersion = '26.0.2'
     testSupportLibraryVersion = '0.5'
     supportLibraryVersion = '27.0.0'
@@ -28,7 +31,6 @@ project.ext {
     junitVersion = '4.12'
     truthVersion = '0.39'
     robolectricVersion = '3.7.1'
-    releaseVersion = '2.7.0'
     modulePrefix = ':'
     if (gradle.ext.has('exoplayerModulePrefix')) {
         modulePrefix += gradle.ext.exoplayerModulePrefix

demos/cast/build.gradle

@@ -19,6 +19,8 @@ android {
     buildToolsVersion project.ext.buildToolsVersion
 
     defaultConfig {
+        versionName project.ext.releaseVersion
+        versionCode project.ext.releaseVersionCode
         minSdkVersion 16
         targetSdkVersion project.ext.targetSdkVersion
     }

demos/cast/src/main/AndroidManifest.xml

@@ -14,12 +14,10 @@
      limitations under the License.
 -->
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.google.android.exoplayer2.castdemo"
-    android:versionCode="2700"
-    android:versionName="2.7.0">
+    package="com.google.android.exoplayer2.castdemo">
 
   <uses-permission android:name="android.permission.INTERNET"/>
-  <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="27"/>
+  <uses-sdk/>
 
   <application android:label="@string/application_name" android:icon="@mipmap/ic_launcher"
       android:largeHeap="true" android:allowBackup="false">

demos/ima/build.gradle

@@ -19,6 +19,8 @@ android {
     buildToolsVersion project.ext.buildToolsVersion
 
     defaultConfig {
+        versionName project.ext.releaseVersion
+        versionCode project.ext.releaseVersionCode
         minSdkVersion 16
         targetSdkVersion project.ext.targetSdkVersion
     }

demos/main/build.gradle

@@ -19,6 +19,8 @@ android {
     buildToolsVersion project.ext.buildToolsVersion
 
     defaultConfig {
+        versionName project.ext.releaseVersion
+        versionCode project.ext.releaseVersionCode
         minSdkVersion 16
         targetSdkVersion project.ext.targetSdkVersion
     }

demos/main/src/main/AndroidManifest.xml

@@ -15,15 +15,13 @@
 -->
 
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.google.android.exoplayer2.demo"
-    android:versionCode="2700"
-    android:versionName="2.7.0">
+    package="com.google.android.exoplayer2.demo">
 
   <uses-permission android:name="android.permission.INTERNET"/>
   <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
   <uses-feature android:name="android.software.leanback" android:required="false"/>
   <uses-feature android:name="android.hardware.touchscreen" android:required="false"/>
-  <uses-sdk android:minSdkVersion="16" android:targetSdkVersion="27"/>
+  <uses-sdk/>
 
   <application
       android:label="@string/application_name"