Ability to get plugin option string in plugin API

compiler/plugin-api/src/org/jetbrains/kotlin/compiler/plugin/CommandLineProcessor.kt

@@ -34,4 +34,8 @@ public trait CommandLineProcessor {
 
     [throws(javaClass<CliOptionProcessingException>())]
     public fun processOption(option: CliOption, value: String, configuration: CompilerConfiguration)
+}
+
+public fun getPluginOptionString(pluginId: String, key: String, value: String): String {
+    return "plugin:$pluginId:$key=$value"
 }