easy configuration system

[yoe]

Once everything has been converted to SReview::Config, we should add an easy way to configure things. Options are:

• Have a separate program to generate/update a configuration file
• Add a page to the admin interface to configure things

Should also consider whether (part of) the configuration should be stored in the database

[yoe]

Separate program written, exists as sreview-config. That should be good enough for now, we can leave the rest for later if we really really want to

[yoe]

For clarity: the wontfix label is there because I'm not going to spend more time on this for now; the help wanted one is because I think it still makes sense (even though it'll have low priority for me) and I'll still take patches.