added kotlin plugin for successfull compilation

proj.android-studio/app/build.gradle

@@ -1,4 +1,5 @@
 apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
 
 android {
     compileSdkVersion 28
@@ -45,4 +46,6 @@ dependencies {
     implementation 'com.android.support:appcompat-v7:28+'
 
     implementation project(':SalmonEngineAndroid')
+
+    compile "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 }

proj.android-studio/build.gradle

@@ -1,6 +1,7 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
+    ext.kotlin_version = '1.2.70'
     repositories {
         jcenter()
         google()
@@ -8,6 +9,7 @@ buildscript {
     }
     dependencies {
         classpath 'com.android.tools.build:gradle:3.2.0-alpha18'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files