vertthrasher retextures phong fix

vertthrasher retextures were very good back in the day, there are some I still use, however, they never had phong, and nobody ever tried to fix it, so I decided to give it try with the bugbait, the crossbow, and the gravity gun. Also tweaked the alpha mask on the crossbow and added a normal map for the gravity gun.

It is not much, but hope you like it. Verttrasher´s gravity gun skin is still the best around here.