#1196 [WIP] Hotfix for edit/override all in DCG (state: open)

This pull request must merged to if DCG has the feature "uniformTime" override/edit all

https://github.com/contao-community-alliance/dc-general/pull/359

@zonky Don´t edit the label of this pull request show in the commit. This isn´t only for uniform time.

na jut

@dmolineus @discordier I have remove the hidden dependency

This change request modifies interfaces so we have backward compatibility issues here. Probably better to add it only for MM 2.1. Wdyt @discordier?

As there are default values on the interface, any existing concrete class should still work.

However should trigger an deprecation notice if not given.

@discordier I put the deprecated notification in an if statement and change the default timestamp value from 0 to null

@dmolineus, @stefanheimes could you re-evaluate this PR and either approve or request changes?