automate the tests more

[GitMensch]

The testing framework is what currently stand out when compared to GixSQL. It would be good to include it in the "autotools way":

• if not done already: add tests/README or similar that specifies in detail what is needed to run the testsuite
• change tests/Makefile to tests/Makefile.am and the subdirs in root to let the testsuite be updated and build automatically; and also be run with make check in the root dir
• if not done already: do the setup (= test db creation) via a shell script, allowing the connection details to be specified via environment it is fine to have a default that matches your test environment)
• if necessary: add check-hook and friends to this Makefile.am to do the necessary setup

I could have a look at doing this, possibly in May 2022.