Version 2.0 of the Solid Test Suite

Hi all,

Thanks to a generous grant from NLNet Foundation <https://nlnet.nl>, I was
able to write version 2.0 of the Solid test suite. Building on Kjetil
Kjernsmo's excellent work on the test suite so far, I split it into three
parts:

* WebID Provider (the system-under-test should have a user 'alice' and the
tester will log in, obtain a cookie, and then use that cookie to go through
the webid-oidc dance in a testnet).

* Solid CRUD (POST/PUT/PATCH to create a container or non-container
resource, GET to read it back, PUT or PATCH to update it, and DELETE to
delete it). This also tests the websockets-pubsub protocol (Updates-Via).
The tester will send authentication credentials using the new `auth`
command, but not test what happens when it's omitted.

* Web-Access-Control (a second system is added to the testnet, and Alice
will edit the ACL docs on her pod to give Bob various kinds of access).

The test suite only tests positive results on the happy path. It tests
whether all Solid server implementations react in the same way in reaction
to correctly functioning Solid apps.

It does not test how the server fails or reacts if the client
misbehaves. There is only one exception to this: the WAC tests, which
(obviously) do check if the server denies access to Bob when Alice's ACL
docs tell it to do so.

So far, the test suite is used in continuous integration by 3 independent
Solid Server implementations:

* node Solid Server (NSS)
* PHP Solid Server (PSS) + the related "Solid" app for Nextcloud
* Community Server (CSS)

And coming soon: Inrupt ESS and TrinPod.

I will now be moving on to other projects (mainly the MoneyPane in Solid
OS) but be available in https://gitter.im/solid/test-suite when needed.

I'll hand over the main day-to-day work to our newest Test Suite panel
<https://github.com/solid/process/blob/master/panels.md#index-of-panels>
member, Pete Edwards - welcome, Pete!

See https://github.com/solid/test-suite for more info, and please join
Pete, Sarven, Yvo and me in https://gitter.im/solid/test-suite.

Happy hacking!
Michiel