Adds and uses a modified_by property in models/work.py This property is used to display the user who last edited the work in the document viewer. Fixes author being set on every edit. Also edited the style-sheet to fix issue i128. Patch by: Lennard de Rijk

from query import *
from subqueries import *
from where import AND, OR
from datastructures import EmptyResultSet

__all__ = ['Query', 'AND', 'OR', 'EmptyResultSet']