CLI: improve diagnostic message format

- render the whole line where the error/warning points to, if any, and another
  line with '^', like other compilers do
- lowercase diagnostic severity
- decapitalize the message if it doesn't start with a proper name

jps-plugin/src/org/jetbrains/kotlin/compilerRunner/CompilerOutputParser.java

@@ -161,7 +161,7 @@ public class CompilerOutputParser {
                 reportToCollector(text);
             }
             else {
-                messageCollector.report(category, text, CompilerMessageLocation.create(path, line, column));
+                messageCollector.report(category, text, CompilerMessageLocation.create(path, line, column, null));
             }
             tags.pop();
         }