Improve usability and validation for website URL fields

On CiviCRM profiles, where there is a website or link field, clicking into the field automatically inserts: http://
into the field.

I'm sure this is done with the best intention, but it is not good for usability. If someone clicks in to the field and then pastes a link, you end up with:
http://https://mysocialmedialink.com

The above (invalid URL) passes validation, whereas www.mysocialmedialink.com does not, giving the not-very-useful message: 'Enter a valid Website.'

Proposed changed

• Do not auto-fill the fields with http://
• Improve the validation error message to say 'Please include the http:// or https:// at the beginning of the URL'. Or something similar.
• (Improve validation for website addresses to allow the umlaut, for example) - CRM-15975

Further reading: http://forum.civicrm.org/index.php?topic=36464