Fix blur glsl shaders and make them independent of the screen resolution

We were not taking the full number of texture taps previously
Reduce the default value of r_bloomBlur

Higher values cause ugly blur artifacts
Fix bloom
‘Fix’ building shadows with cg_Shadows < 2.
Add fast shadow blur for variance shadow maps

One of the advantages of variance shadow maps is you can use a simple blur filter over the texture for a cheaper PCF-like effect
Fix potential shadow casters being light frustum culled
Fix backside culling for shadow blur
Fix atan/atanf in qvms
Merge remote-tracking branch 'remotes/origin/master' into gameplay/master
Merge branch 'gameplay/master' into gameplay/viech