Allow changing of crosshair size + fixes

* vr_crosshair_size allows setting size of vr crosshairs from 1 to 5
points diameter
* Added VR_SetAngels() to allow properly setting view angles without
messing with aim modes
* Now retain entire last orientation and aim vectors
* Fix issues related to intermission direction with some aim modes
* Fix issues related to resetting HMD orientation with certain aim modes
Only draw crosshair if player is alive