Improve group and host deployment support

[grtjn]

Recent changes allow adding @group on appservers and databases. It also creates groups if they don't exist yet. Unfortunately it doesn't assign hosts to those new groups, so databases assigned to those new groups end up without forests.

I recommend improving config by wrapping the relevant appservers inside gr:groups/gr:group with a gr:group-name that shows in which group those should be added. This provides space for setting group properties as well. Additionally a ho:hosts/ho:host structure needs to be added that allows setting host properties which also includes assigning a host to a group.

It is possible to rewrite configs on the fly to support backwards compatibility, and put appservers and database forest in Default group (or the one of the current host/app-server) if not explicitly specified.

[grtjn]

I have worked on this, and managed to get bootstrap and wipe working with this. Works nicely with the previous work on assigning servers and database forests to (hosts within) groups.

Only one catch that admin:group-delete refuses to delete a group even after saving config. Apparently a restart is necessary to refresh results returned by xdmp:groups and xdmp:group-hosts, which is used inside the admin function to verify if admin-config has been saved properly. I worked around that by bailing out early, and telling the user to restart and wipe again.

I will open a pull request for review..

[grtjn]

It does extend on #307, so maybe review that first..

[grtjn]

Fixed in dev