Added a check to see if the date about to be parsed is a Date

Added a check to see if the date about to be parsed by Globalize is already a Date, and if so return the current date without parsing (which would likely return null when trying to parse a UTC date with a format pattern of dd/MM/yyyy).

This fixes an issue where if a date is set programatically by either the DatePickerRange or a call to setUTCDate(s) the new value is ignored and the DatePicker resets to the current date.

---------- To Replicate Issue -----------
1. Setup Globalize with locale like en-GB
2. Add bootstrap-datepicker.js to scripts
3. Add bootstrap-datepicker-globalize.js
4. Add a DatePickerRange to a page.
5. Try use datepicker - selected dates are ignored and today's date is always selected.