Extend conditional mappings with more complex rules

[jimkont]

For now, this is what we support for conditional mappings: [1]

we would like to extend the syntax to allow more complex conditions (like &&, ||, !). A discussion on this can be found in [2].

[1] http://mappings.dbpedia.org/index.php/Template:Condition [2] https://sourceforge.net/mailarchive/message.php?msg_id=30541656