* brushexport plugin fix: invert Y during YZ swap; invert V of UV coords (correct texturing)
* brushexport plugin: default to 'Don't collapse' option
q3map2: * obj export: save in popular 'Y = Up, -Z = Forward' format
* picomodel::obj: load as popular 'Y = Up, -Z = Forward' format
* picomodel::obj: fix support of back references in faces