IPAAnsibleModule: Provide base configuration for delete_continue.

Allows the creation of IPAAnsibleModule objects with specific
`ipa_arguments` which are defined in a dictionary of argumets in
the base class.

Every module using `delete_continue` should provide the proper behavior
and the module must be instantiated with:

  ansible_module = IPAAnsibleModule(
      ...,
      ipa_arguments=["delete_continue"]
  )

The plugin documentation must be extended with
'ipamodule_arguments.delete_continue'.

plugins/doc_fragments/ipamodule_base_docs.py

@@ -45,3 +45,13 @@ options:
     type: bool
     default: true
 """
+
+    DELETE_CONTINUE = r"""
+options:
+  delete_continue:
+    description: |
+      Continuous mode. Don't stop on errors. Valid only if `state` is `absent`.
+    aliases: ["continue"]
+    type: bool
+    default: True
+"""