[OpenAPI] unindex/remove operations accept URIs via form data and not just query

[Enet4]

The Web API specification in dicoogle_web_api.yaml suggests that the operations /management/tasks/unindex and
/management/tasks/remove receive all input via the query string. This would be accepted by Dicoogle, but the URIs to unindex or remove are preferably passed as a form data object (url-encoded) so that they do not make the URI too long. This has been the case since Dicoogle 2, so the specification is missing this particular detail.

The operations mentioned above should be documented so that they accept multiple URIs via form data, and that users should prefer this way of passing the uri parameter over passing it via the query string.