Open files with errors in external editor

This pull request makes it possible to open compilation errors in an external editor at the correct line.

A URL can be configured via the extensions' "Options..." page (in the Chrome extension list), with the absolute path to the file and the line number . This can be taken advantage of by external editors to directly jump to the file and line.

For IntelliJ IDEA, the RemoteCall plugin (https://github.com/Zolotov/RemoteCall#readme) can be used. In this case the URL to be configured would be `http://localhost:8091?message=$file:$line`