Port doc printer to Kotlin, heavily improve

worldedit-core/doctools/build.gradle.kts

@@ -0,0 +1,19 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+    kotlin("jvm") version "1.3.31"
+}
+
+tasks.withType<KotlinCompile> {
+    kotlinOptions.jvmTarget = "1.8"
+}
+
+repositories {
+    jcenter()
+}
+
+dependencies {
+    "implementation"(project(":worldedit-libs:core:ap"))
+    "implementation"(project(":worldedit-core"))
+    "implementation"(kotlin("stdlib-jdk8"))
+}