WIP: update default denomination and instructions for regression tests
Because I was running into problems setting up the testing environment, I used the experience to update the instructions in the README file and to care about the very generic names "myempty" "mycaldav".
I used the virtual host setup from the readme, which requires only a single testing domain (that differs from the wiki explanation on https://wiki.davical.org/index.php/Developer_Setup) by using an alias for subfolder testing.
The default testing domain is now the more generally valid http://davical-testing.localhost. Also the default database name is now davical_testing.
Above all, the testing readme is rewritten in several places to make it easier to set this up and duplicate code fragments are removed.
- update the wiki about development setup
- still the example files are named regression, its not clear if there should be seperated between "regression" and "testing"
- the regression.conf still contains different vars for main and subfolder domain
- the gitlab CI/CD is failing, but I don't think this is because of the changes, a more general problem?