Rejigger configs
The following commit series does the following:
- fix an off-by-one in the migrations version scheme. @phyks, can you have a look please?
- don't send some config pairs twice: those are all the config pair "deducted" from Kresus at runtime, and in the rare case where somebody exports/imports their instance, they'll see the deducted config pairs, which I call "ghosts" here. @nicofrand, can you have a look and confirm it fixes your issue? Or @ZeHiro as you reported it?
- renames the Weboob tab in the settings "admin" and moves the email configuration below "admin" too. This paves the way towards having regular vs admin users, in a multi-user setting.
- allows removing an SMTP configuration, and display a message to the user when they're trying to set an alert / report email but they haven't configured SMTP first.
Of course, everybody is encouraged to look at all these commits. I've manually tested all of them for some time, and I think they should be at least functional.