Bugs fixed and Improvements

Fixed bug in Background Features: Calculated Expression is saved even if Cancel is clicked in field settings dialog

Now configuration is deleted or not saved after cancelling.

Fixed localization issue with Calculated Expressions: date fields not working properly on site with German localization

Previously where errors for dates greater than 12. 

"X-RequestDigest" request header now is configurable for HTTP Request action type

Header became optional. For previously configured HTTP request actions was added by default.