Various improvements and fixes - incl. VDB loaders, better FPS checks in Houdini

[BigRoy]

Overview of changes

Loader

• Implement VDB for V-ray Loader in Maya - now works correctly!

• Implement VDB for Redshift Loader in Maya - now works correctly!

• Implement VDB for Arnold Loader in Maya - new.

• Implement VDB Loader in Houdini

• Implement Set Frame Range actions in Loader in Houdini

• Improved Copy File Path / Copy Path sorting so they are less intertwined with other actions in the Loader

• Changed Copy File Path / Copy Path icon colors for less clutter.

• Improved Loader Maya "Import Model" warning message so it describes that it will import it as unlinked to Avalon pipeline.

• Houdini Loaders, simplify loaded name - remove _001 counter that didn't work anyway + remove _CON suffix.

FPS + Outdated Scene Pop-ups

• Implement Houdini set asset FPS on "new scene.."

• Implement Houdini set asset FPS on launch (so startup scene has correct FPS)

• Fix code readability with generic Popup class

• Fix FPS popup Maya "update keys" checkbox actually doing something. :) (Oh my god, that code that was there... lol)

• Fix FPS popup not being positioned correctly in rare cases.

• FPS popup now shows what current FPS is and what it will change it to. So it shows current FPS and project FPS.

• FPS popup in Houdini title stating "Maya scene", now shows "Houdini Scene"

• Outdated Assets in Scene message in Houdini stating "Maya scene" now shows "Houdini Scene"

Houdini Publishing

• Added File Extension validator: ensure output path actually generates correct file extension in ROP node.
• Refactored "Validate Animation Settings" to "Validate Frame Tokens" to be more explicit about what it does.
• Added clarification in error message of "Validate Input Node (VDB)" when SOP path is not set on ROP.