Warmup command functionality broken

[Qup42]

• Most of qlever-ui's commands warmup commands issue require an access token. Warmup commands don't include an access token in the requests to the back end even if one is defined. This applies to the management command as well as the HTTP API.
• The HTTP API for calling warmup commands uses a hard coded token for access control. This has no security impact, because the underlying functions don't work. Still this is bad practice and should be fixed.