JS backend: LibrarySourcesConfig accepts source dir as source.

Idea send files in any case, but for easy debug run configurations we want to specify only source dir.

(cherry picked from commit e194435)

compiler/cli/src/org/jetbrains/jet/cli/js/K2JSCompilerArguments.java

@@ -24,13 +24,11 @@ import org.jetbrains.k2js.facade.MainCallParameters;
 
 /**
  * NOTE: for now K2JSCompiler supports only minimal amount of parameters required to launch it from the plugin.
- * You can specify path to the file where generated file will be stored, path to zipped library sources.
  */
 public class K2JSCompilerArguments extends CompilerArguments {
     @Argument(value = "output", description = "Output file path")
     public String outputFile;
 
-    //NOTE: may well be a subject to change soon
     @Argument(value = "libraryFiles", description = "Path to zipped lib sources or kotlin files")
     public String[] libraryFiles;