Small utility to report on OS version and other useful information

[Athanasius]

Given issues like #798 it might be useful to have a small utility to gather key points of information about a user's system:

1. OS version.
2. Hardware (if there's an easy, non-intrusive way to get at this, else we'd need to ask a user to run some third-party util).
3. Locale + encoding.
4. Check that the expected journals location actually contains journal files.
5. Check expected log destinations can be accessed (create and truncate files).

Anything else we can think of. This utility would need to be as paranoid/bare bones as possible, e.g. it would be no good using our logging in it if our logging can cause issues.

[Rixxan]

Took a swing at this in 763d8cc.

Seems to work pretty well in both Linux and Windows from what I've been able to test (thanks, WSL!)

Opinions and feedback welcome :)