modified date property should be on each version

[pawelotto]

I think it's extremely important to store modified date property not only on the main version object but also on every single version sub objects, otherwise it's impossible to track changes in time.

If you have no time please tell me I'd fork and pull-request this.

Thanks!

[saintedlama]

Hi, I have no time asap to implement that feature. Could you send me a pr

[pawelotto]

Sure, will do it along with this issue