Create a 'Current Status' fieldset for the availability checkbox and date field

Within the wsuser module, move the checkbox and date fields to their own
fieldset in order to emphasize them. RE: Issue #357
Add conditional highlighting to 'Current Status' fieldset if user's unavailble.

Highlight the 'Current Status' fieldset, which contains the availability
checkbox and date field, if 'Not Currently Available' is checked.
RE: Issue #357