Come August 4-7, FPS fans will descend in droves upon QuakeCon, a celebration of all things headshot-related in Dallas, Texas. And while FPSes have come a long way since those blocky days, one of the biggest headliners at this year’s con is the reborn Tribes, a favorite with the FPS faithful since the days when you had to push you PC to run Quake instead of playing it in a browser. The new title, Tribes: Ascend (because jetpacks), will be playable for the first time at QuakeCon, and attendees can enter for a chance to go into the free-play game’s closed beta… …