Add startup script for testing purposes

[RubenVerborgh]

The security setting associated with Node 8 compatibility (#518) means the server will only work with trusted certificates. To avoid this for testing purposes, the NODE_TLS_REJECT_UNAUTHORIZED environment variable should be set.

In order to facilitate that, this pull request adds a bin/solid-test executable. For consistency, it also renames the default executable to bin/solid from bin/solid.js, but the latter is symlinked.

Open questions:

• Is solid-test an appropriate name? I thought of alternatives such as solid-insecure, but that seemed to strong. In any case, the executable is not exported in package.json.
• Where should documentation for this feature be added? (In any case, to the changelog [Update CHANGELOG for version 4.0.0 #534].)

[dmitrizagidulin]

I think naming it solid-test would carry across the right connotation. (We can also automatically prepend the DEBUG="solid:*" env variable, too, while we're at it).

As for documenting, aside from the CHANGELOG, I think we should also add it to the README, in the Command Line Usage / Running a Server sections. What do you think?

[dmitrizagidulin]

I'm also not sure whether it's worth leaving solid-test out of the npm scripts..

[RubenVerborgh]

(We can also automatically prepend the DEBUG="solid:*" env variable, too, while we're at it).

Maybe not, as people might like to make their own, more specific settings?

I think we should also add it to the README, in the Command Line Usage / Running a Server sections.

Will do!

I'm also not sure whether it's worth leaving solid-test out of the npm scripts.

Well, there's scripts and there is bin. I don't think it has a place in bin, but maybe in scripts. Then the question is what script? I thought about start (as this is commonly used), but there's also already a solid entry. Maybe a solid-test entry then?

[RubenVerborgh]

@dmitrizagidulin Documentation added, ready for review.

[dmitrizagidulin]

Excellent, thanks.