Refactor settings

[TamaraGunkel]

To ensure backwards compatibility with older block versions, the tool still uses the old settings like apiurlwithout the instanceid (apiurl_1). We should drop this behaviour in favor of more clean and reliable code. A good way to do that, would be to change this with the first release for Moodle 4 because all universities will probably upgrade the all plugins.

[ferishili]

FIxed and merged via 91b6fc9