Improve accessibility

[Info 3bits]

Fix issues displayed in WCAG and HTML validators:

• Missing form labels
• Empty <a> tags (course tiles)
• FA icons accessibility
• Search box icon
• Announcements Play/Pause icon
• Breadcrumb (alt)

And follow some other UI/UX advices:

• Cancel button to link

Links to verify the issues:

WCAG http://wave.webaim.org/report#/https%3A%2F%2Fadaptable.ws%2Fdemo%2F

HTML http://www.htmlhelp.com/cgi-bin/validate.cgi?url=https%3A%2F%2Fadaptable.ws%2Fdemo&warnings=yes