Assure user rights for deployed branches

This PR allows that multiple users can deploy the same branch.

Before, it was not possible because when user x deployed the branch, then user y didn't have the rights to update/delete the deployed branch on mf1lt /var/www... directories.

I tried to do this with the following, but it was not working:
```
git config core.sharedRepository true
npm config set group geodata
npm config set umask 0002
```

Note: I suspect the same will be relevant for our standard deployment, but this fix is limited to the deploybranch target.