(Vancouver, WA)  --  Friends and family members are paying tribute to a transgender teenager believed to have been murdered.  A public vigil is scheduled at five o'clock tonight for 18-year-old Nikki Kuhnhausen.  Police have arrested 27-year-old David Bogdanov on a charge of second-degree murder for her death.  Investigators believe Bogdanov killed Kuhnhausen after she revealed to him that she'd been born male.  The two had reportedly been