Add support for install_config with class_nodelete

[23doors]

So far it's only on staging but there is a new field for socket installation: install_config with one possible flag class_nodelete.

If you specify: install_config={"class_nodelete": true} then no class/class fields deletions will be allowed and you would get status='prompt' and error about it in status_info field:

Irreversible class changes:
Classes: "class_1", "class_2" are about to be deleted.
Fields: "field_1", "field_2" of class ""class_3" are about to be deleted.
Fields: "field_1" of class ""class_4" are about to be deleted.

This is to prevent accidental class/field deletions. CLI should always define: install_config={"class_nodelete": true} and if it ends with status=prompt, show status_info and ask user to confirm. And if user confirms, send install_config={} or explicitly install_config={"class_nodelete": false}.