merge 4.0.1.x branch to master: make snippet component versioning

[joshyu]

Hi team,

Recently we are about to upgrade our CMS version to 4.1.2, but we still need the feature of making snippet versioning. Currently all of the versioning related changes are in the branch support/django-cms-4.0.x. Is it possible to merge this branch to master? we can cherry-pick and merge every meaningful changes.

@fsbraun , @Aiky30 ,
please provide your input.

[fsbraun]

@joshyu what's your opinion on #160? Snippets for everyone?

[joshyu]

@fsbraun,
Cool. I missed this PR. it's just what we want.
I will give it a test and give you my feedback.

[joshyu]

Hi @fsbraun ,

I installed this PR branch to djangocms-quickstart for a test, but failed to build web image.

I found that the template folder and internal files are missing from the directory tree.

Can you please check it?