Improve running tests locally

[edmondchuc]

Proposed Changes

• Add running tests instructions to README
• Simpler on-boarding experience for contributors who want to contribute and run tests locally with the options to run the tests on the host system or in a Docker test running environment.
• Fixes OSError: [Errno 49] Can't assign requested address on some OSs such as macOS.
• Removes the requirement to have BerkeleyDB installed on the host system (problematic for macOS and Windows users).

[nicholascar]

Good additions @edmondchuc. There has been a lot of work for the "cannot assign address" using Mock SPARQL endpoints, instead of DBPedia and in auto-allocating free local IP addresses, but I'm not sure if they are all merged yet. I don't think this container work will get in the way of that so I think this is good to go.

[aucampia]

Good additions @edmondchuc. There has been a lot of work for the "cannot assign address" using Mock SPARQL endpoints, instead of DBPedia and in auto-allocating free local IP addresses, but I'm not sure if they are all merged yet. I don't think this container work will get in the way of that so I think this is good to go.

Please do ping me if you get any more spurious failures from tests so I can have a look, as far as I know they should be gone in master now and in forks that are up to date with master.