BalloonEval: escape double quotes and new line characters

[gagara]

Escape " and \n characters in BalloonEval selection.
Fixes #460

[puremourning]

This change is 

[puremourning]

Thanks for sending a patch!

Please can you elaborate on the rationale for this approach and how you tested it and confirmed it works and doesn't regress?

[gagara]

If we consider following code snippet

        String s = "line1" +
            "line2";

if we try to evaluate either "line1" or both "line1" + "line2" then we will get an error (see #460).
This fix should allow mentioned evaluations.
Unit tests are green, that is why I expect no regression.