#11, #16

* #11: A simple (just syntax highlighting, no fancy stuff like Outline view support) and hopefully very fast JavaScript editor. Shamelessly copied over from the now-inactive ChromeDevTools-Java. Should be useful given that the JavaScript output of GWT in SuperDevMode is a single enormous JS file. 
* #16: Native SDBG JavaScript breakpoints are supported in the above JS editor.
* The SDBG JS breakpoint icons are corrected to be smaller and match in appearance the JDT breakpoint icons. The previous shockingly bigger ones were inherited from the Dart editor.