Migrate to Kotlin (#76)

Kotlin is mature enough at this point, and is the direction
Android development has gone in.

.gitignore

@@ -6,3 +6,4 @@
 /build
 /captures
 .externalNativeBuild
+.kotlin

app/build.gradle.kts

@@ -0,0 +1,51 @@
+plugins {
+    id("com.android.application")
+    id("org.jetbrains.kotlin.android")
+}
+
+android {
+    namespace = "org.cuberite.android"
+    compileSdk = 34
+    defaultConfig {
+        applicationId = "org.cuberite.android"
+        resourceConfigurations += listOf("en", "de", "nl", "pt", "zh_CN")
+        minSdk = 16
+        //noinspection ExpiredTargetSdkVersion
+        targetSdk = 28
+        versionCode = 15
+        versionName = "1.6.3"
+        vectorDrawables.useSupportLibrary = true
+    }
+    buildFeatures {
+        buildConfig = true
+    }
+    buildTypes {
+        getByName("release") {
+            signingConfig = signingConfigs.getByName("debug")
+        }
+        named("release") {
+            isMinifyEnabled = true
+            isShrinkResources = true
+            proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
+        }
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+    kotlinOptions {
+        jvmTarget = "17"
+    }
+}
+
+dependencies {
+    implementation(fileTree(mapOf("dir" to "libs", "include" to listOf("*.jar"))))
+    implementation("androidx.appcompat:appcompat:1.6.1")
+    implementation("androidx.core:core-ktx:1.12.0")
+    implementation("androidx.fragment:fragment-ktx:1.6.2")
+    implementation("androidx.localbroadcastmanager:localbroadcastmanager:1.1.0")
+    implementation("androidx.preference:preference-ktx:1.2.1")
+    implementation("androidx.vectordrawable:vectordrawable:1.1.0")
+    implementation("com.google.android.material:material:1.10.0")
+    implementation("org.ini4j:ini4j:0.5.4")
+}