Improving HBAO2, SSAO1, SSAO2.

HBAO2: added check on tangent for angle above 90°.
Problems when radius is small: 'tVector' is parallel to the normal
and we get a random tangent which does not follow 'direction'.
Solution: calculate 'vector' not with 'vectorUV' (which could be
less than a texel) but with 'texelStep': one exact texel step.
Same problem with 'sampleTexCoord', when noise.z is small it can't
follow the direction and snapping only make it worse.
Solution: make the first 'sampleTexCoord' to move of a texel at
least, same for the step 'sampleStep' but zero here shouldn't be
a problem.

SSAO1: again, make 'sampleTexCoord' move of a texel at least.

SSAO2: problems with flat surfaces, added a bias but it is not
enough. Again the problem arises when cRadius is small.

Removed '#version', GLSL compiler complains it is not the first
instruction.
Deal with DropDownList generating a ListView::E_ITEMDESELECTED but not
a DropDownList::E_ITEMSELECTED when SetSelection is called.
Restored the original DeferredLight shader, it is still a good place to
manage occlusion in shadows and occlusion in light.
Added a shader AOmerge to mix the occlusion based on the pixel luminance.
Comments on the shader. Move SSAO3 near SSAO1. HBAO2 still has artifact
due to the tangent factor tangentSign, tried to cancel it if occlusion
is below 0.02, no good (better to use the original screen oriented shader).
Cleaning.