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

compiler/testData/cli/jvm/pluginSimpleUsage.out

@@ -1,8 +1,8 @@
-ERROR: Required plugin option not present: org.jetbrains.kotlin.android:androidRes
+error: required plugin option not present: org.jetbrains.kotlin.android:androidRes
 
 Plugin "org.jetbrains.kotlin.android" usage:
   androidRes <path>          Android resources path (required, multiple)
   androidManifest <path>     Android manifest file (required)
   supportV4 <path>           Support android-v4 library
 
-COMPILATION_ERROR
+COMPILATION_ERROR