Sort values in multi-select widgets.
More robust XLS export code.
Fix error introduced by my previous commit.
audit: added method to determine if an item is auditable (factorization)
audit: if auditing should fail don't let errors propagates
audit: changes on an entity related model (needed for complex and multiple values) can be attached on entity audit
updated sqlalchemy to 0.8, wtform 1.0.4 and wtforms-alchemy to 0.7.15