Implement rain in hardware renderer.
Implement snow in hardware renderer.

Also raised the emitter height for rain and snow, to make it look more
realistic.
Server infrastructure for snow/rain.

Qormas will now also activate snow in all rooms by default.
Add preferences menu option to turn weather off.

In both English and German clients.
Increment client minor vers  to 17
Add small amount of x velocity to snow.

Recommendation from Keen.
Rain/snow refactor, particle effect bugfix, CV window transparency.

Refactored the code for rain/snow and made a lot of adjustments.
Fixed a bug that was preventing random particle position from being
truly random.
Made the windows in CV main room properly transparent so weather effects
happening outside can be seen.