Merge pull request #67 from wardi/master

metadata schema: eliminate some duplicate departments
add checkboxes for subject/topic_categories
fix: field descriptions are available in french now
don't shadow jinja2 builtin kwargs
better docs for canada_form macros, remove unused default
refactor multi_checkbox_field to be used like other widgets
multi_checkbox_field parameter docs from form.select
consistent macro documenting style
formfield: remove needless check for unset widget