How to migrate from janchor to pyrss.

- Turn off janchor.

- Copy janchor_convert.py to /var/lib/janchor (or wherever 'sources' and
'registrations' files are placed) and run it. Two files should get generated:
'sources.sql' and 'registrations.sql'.

- Configure pyrss to use the same address as janchor did and initiate it's
database.

- Import the content of 'sources.sql' into pyrss' database.

- Run pyrss and wait until none of the 'last_time' fields of 'addressess' table
equals zero.

- Turn off pyrss.

- Paste the content of 'registrations.sql' into pyrss' database.

- Run pyrss.

And that's it.

Do note, that I (Mariusz Mazur) have also changed users' subscriptions to
'both' for all rss sources (janchor doesn't require that while subscribing),
but I'm not sure if it's required when modifying pyrss' database directly, as
we just did.

