Convert thrifty-java-codegen to Kotlin (#173)

As part of the prep work for implementing Kotlin codegen, we're converting the compiler to Kotlin. This is the first portion to be converted; thrifty-schema is next, in stages.

build.gradle

@@ -28,6 +28,8 @@ allprojects {
     version VERSION
 
     project.ext {
+        kotlin_version = '1.2.41'
+
         libraries = [
                 guava: [
                         'com.google.guava:guava:23.0'
@@ -41,6 +43,10 @@ allprojects {
                         'com.squareup:javapoet:1.11.1'
                 ],
 
+                kotlin: [
+                        "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+                ],
+
                 testing: [
                         'junit:junit:4.12',
                         'org.mockito:mockito-core:1.10.19',
@@ -62,6 +68,7 @@ buildscript {
 
     dependencies {
         classpath 'net.ltgt.gradle:gradle-errorprone-plugin:0.0.14'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.2.41"
     }
 }
 

gradle.properties

@@ -1,5 +1,5 @@
 GROUP=com.microsoft.thrifty
-VERSION=0.4.4-SNAPSHOT
+VERSION=0.5.0-SNAPSHOT
 
 POM_URL=https://github.com/microsoft/thrifty/
 

gradle/wrapper/gradle-wrapper.properties

@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.3.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.7-all.zip

thrifty-java-codegen/build.gradle

@@ -18,6 +18,9 @@
  *
  * See the Apache Version 2.0 License for specific language governing permissions and limitations under the License.
  */
+
+apply plugin: 'kotlin'
+
 description = 'Converts Thrifty Schemas into Java source files'
 
 dependencies {
@@ -26,6 +29,8 @@ dependencies {
     api libraries.okio
     api libraries.javaPoet
 
+    api libraries.kotlin
+
     implementation project(':thrifty-runtime')
 
     testImplementation libraries.testing