Improve auto UI generation

Auto UI generation is made for all native Arnold shaders by the help of a metadata file called `arnold_shaders.mtd`. Some features would be good do add to that auto generation:

**Tabs**
Auto UI generation currently lacks the function to create Tabs.
This would come in handy if we want to implement ID AOVs #10

**Disabling**
The arnold_shaders.mtd has a lot of disable expressions like
`soft.disable_when STRING "{ material != custom }"`
but there's currently no support for it in the auto generation code.
This should also be implemented.

Start by locating the auto-generation entry point that reads arnold_shaders.mtd, then inspect how existing metadata features are handled. Use the issue's soft.disable_when example and the ID AOV reference as input cases. Done means generated native Arnold shader UIs support tabs and disabling expressions.

Written by the indexing model from the issue text.