First commit for 404 (etc) error pages.
Merge pull request #86 from yeastgenome/system-pages

First commit for 404 (etc) error pages.
Fixed resources section to hide headers if there aren't any urls of that type.
Merge branch 'sequence-fixes' into refactoring-templates

Conflicts:
	src/sgd/frontend/yeastgenome/static/templates/sequence_details.jinja2
Merge branch 'master' into refactoring-templates