Xtext tool service does not use trusted origins env variable

[barnettwilliam]

The trusted origins header for the generated editor instance is not set using the TRUSTED_ORIGINS environment variable used elswhere by the platform. Instead, it is hardcoded into:

• platformtools/xtext/acemodebundler/web.xml
• platformtools/xtext/editorserver/scr/config.js

which if not set correctly the deployed editor instances cannot be accessed as the session cookie will not be used so requests for validation and autocompletion will be ignored.