Create www-data and www-user users and groups with a fixed uid/gid

[dol]

This PR allows to predefine the uid/gid of the user www-data and www-user. This fixes a lot of issues like puphpet/puphpet#2757 .

If the uid/gid is fixed the synced_folder option in the puphpet could look like this:

        synced_folder:
            vflsf_wv94qxb0ihgz:
                owner: 2000
                group: 2000
                source: ./
                target: /var/www/mywebproject
                sync_type: default
                ...

The users and group creation can also be overwritten in the config.yaml. E.g.:

server:
    install: '1'
    packages:
        - vim
    groups:
         www-data: 333
         www-user: 444
     users:
         www-data: 333
         www-user: 444

[dol]

I just found out I could do this with

puppet-puphpet/manifests/usersgroups.pp

Line 1 in 70e3f63

class puphpet::usersgroups {

. But I need to add the uid/gid param to this class. Not sure which is the best fit for this feature.

Also make sure, that the user/group www-data is always created. Do this by merging the default value into the users/groups hiera data.

[dol]

Updated PR that the www-data and www-user will be always created.