Update existing Arnold shaders and add car_paint

[JenusL]

Changes made in Arnold 5.0.2:

• new car_paint shader
• standard_surface got new sss mode and anisotropic sss
• standard_surface got transmit_aovs checkbox
• triplanar got cell parameters
• shadow_matte improved (and 2 aovs removed)
• flakes improved

Changes made in Arnold 5.1.0:

• shadow_matte got aov_group parameter
• pref_name added to flakes, noise, triplanar
• P removed from triplanar
• trace_set added to ambient_occlusion
• extra_samples added to standard_hair
• face_mode added to color_jitter
• normal added to passthrough

I can also have changed some min/max, softmin/softmax on shaders where I saw fit. I have used MtoA .mtd file as reference when unsure about those. I've also hidden some Normal/Tangent UI elements so that they only have a port.

[sjannuz]

If you want to complete this, we also had ID AOVs added to standard_surface and standard_hair, and aov_group added to shadow_matte. In the meantime, I'm merging the PR.

[JenusL]

@sjannuz aov_group is added to shadow_matte in this PR :) I know about the ID AOVs but felt that those would need to be on it's own tab in the Shader UI. I don't know if the .mtd have support for Tabs so that would need to be implemented as well. Will create a issue.

[sjannuz]

ops, sorry for missing shadow_matte. Yes, I left tabs out of the auto UI generation based on metadata. Hopefully the code is clean enough, in case we want to add it.

[JenusL]

I had a look at the auto UI generation code and it was pretty clean so it shouldn't be too hard. We should also implement the disable expressions.