Enable Java 8 features in Dolphin

Source/Android/app/build.gradle

@@ -4,6 +4,11 @@ android {
     compileSdkVersion 26
     buildToolsVersion '26.0.2'
 
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
     lintOptions {
         // This is important as it will run lint but not abort on error
         // Lint has some overly obnoxious "errors" that should really be warnings