Formvalid: focus field in error on error message link click

When one of the .errorContainer links is clicked, this will
scroll to the field in error and give focus to the input element.

1. Update `.errorContainer a` click handler with v3.1 code where
   appropriate.
2. Remove preIE7 conditional check as all browsers benefit from this.

Note: this does not need to be merged with master.
Merge pull request #4291 from patheard/formvalid-focus

Formvalid: focus field in error on error message link click