Do not store available workflows preferences in text files

We store available workflows preferences in text files in 'Data Dictionary' now. It is not good in general and may cause issues because of permissions (see ALV-262 for details). So, it's worth remove this legacy scheme and mode to generic alvex:config we have for other extensions.

P.S. Moving http://issues.itdhq.com/browse/ALV-12 to Github Issues.
