warn users on debian if they are running with a non-default user

[benjaoming]

Example:

✗ bin/kalite asdasd
You are not running kalite as the default user ka-lite. This is recommended unless you want to re-create the database and start storing new videos/exercises etc. for a different user account

To run the command as the default user, run this instead:

    sudo su ka-lite -s /bin/sh -c bin/kalite asdasd

Do you wish to continue? [y/N] 

Pressing enter exits, entering y/Y continues. Having something in .kalite makes it skip.

[MCGallaspy]

This one looks pretty critical. Can you add milestones to your PRs when you open them?

[benjaoming]

Sorry, that was a miss. Is definitely intended for 0.14. It was also included in alpha7.

[benjaoming]

Going to make an amendment after a change of /etc/ka-lite layout....

[benjaoming]

So this is ready to be merged, any critical views?

[jamalex]

I think this might interact with some of the stuff @rtibbles was working on, so perhaps he could take a look here as well?

[benjaoming]

So I think this one is definitely a prerequisite for our default debconf flow, @jamalex could you have the final check and merge it? I've tested this already in alpha7 and find that it's "low-risk".

[benjaoming]

This has been part of 5 alpha releases now. Fixed @MCGallaspy 's comments.

Merging now.