[Users] Claws lost my accounts upon -9 kill

[nteodosio at posteo.de]

My computer shut down due to lack of power (note I had no Upower guard 
so it was really a classic "unplugged power line" case). Claws was 
running, as it usually is.

I boot in again and after complaining "address book error, could not 
read address book", it acts like it's the first start, asking me to set 
up my account.

I verify that accountrc is empty, so I substitute it by the 
accountrc.bak, which has a time stamp of just a few hours ago.

Then Claws no longer asks me to register and I do see my accounts in the 
folder list, which have my mail as expected, but every one of them ask 
for its password.

The GUI also reverted to what it looks like the default state.

If someone already had such experience and knows the smoothest way to 
get things recovered to the previous state, I'm glad to hear.

And then I'm also available for further debugging. I cloned the 
.claws-mail directory as of now (minus imapcache) so as to not further 
taint it with my recovery attempts.