fpsVR - 1.7.4

The fpsVR has been updated with the following changes:

• fpsVR now checks the version of SteamVR and offers to switch to the old versions of fpsVR, if the user uses an outdated version of SteamVR
  (this is reworked version of check that was first added in v1.7.1 and later removed in v1.7.3)
  
• Various bug fixes