Small improvements (#22)

* Remove sky color hardcoding

* Bind to available port instead of 25565

* Fix error class and reduce accessors

* Fix language errors

* Cleanup imports and remove weird behaviour

* Print properly message

* Print version name

* Bump gson, update API usage and use linkedhashset over list

* Reimplement approach to categories

* Enable all feature flags by default

* Use jul instead of slf4j

* Call mc repo before maven central to fix build on mac

1.15/build.gradle

@@ -45,3 +45,9 @@ tasks.withType(RemapJarTask).configureEach {
 tasks.withType(JavaCompile).configureEach {
     it.options.encoding = "UTF-8"
 }
+
+java {
+    toolchain {
+        languageVersion.set(JavaLanguageVersion.of(21))
+    }
+}