GUI-489: Add angular-sanitize module and escape unsafe content in tag editor.
GUI-489: Sanitize descriptions on images landing page.
GUI-489: Remove unused content for security group rules display on landing page.
GUI-489: Prevent long tag names from breaking autoscale tag editor (copied from standard tag editor), and escape unsafe content in tag preview.
Merge pull request #326 from eucalyptus/GUI-489

GUI-489: Sanitize unsafe content to prevent XSS attack vectors