Added (deprecated) compatibility shims and general clean-up

  -> Added @getcam_avdistmin=<channel>, @getcam_avdistmax=<channel>, @getcam_fovmin=<channel>, @getcam_fovmax=<channel> and @getcam_textures=<channel>
  -> Added @getcam_avdist=<channel>, @getcam_fov=<channel>
  -> Added @setcam_mode[:<mouselook|thirdperson>]=force

--HG--
branch : RLVa