Initial read-only support for issues.
Add issues to article form.
CSS: fix positioning of checkboxes and their labels.
Merge branch 'master' of github.com:Code4SA/mma-dexter into issues

Conflicts:
	dexter/models/__init__.py
	dexter/models/document.py
	dexter/templates/articles/edit_analysis.haml
Edit Analysis: Flash message on validation error.
Fix validation issues for checkbox multiselect field.
Show Article: render related issues. Display time together with the date info.
Pre-populate issue checkboxes.
Use 'secondary_table' in document-issue relationship.
Update frontend to use new document-issue relationship.
Updates from Greg's comments.
Testing: check that issue can be selected.
Merge pull request #12 from Code4SA/issues

Issues