Update yaml

[pplantinga]

Updates in this PR:

• Add !copy tag for copying objects, rather than making a reference
• Convert ! tag prefix to !new: and add !name: and !module:
• Add !tuple tag for tuples, plus an implicit resolver if a string starts+ends with ()
• Perform simple arithmetic on !ref and !copy nodes for stuff like filter sizes based on block #.
• Remove merge op, anchors, and aliases from speechbrain yaml files.

[Gastron]

I endorse these changes. We've had a lot of YAML discussion the past two days and this is what I think we converged to.

Code looks good to me. Props for the neat arithmetic implementation!