TVPaint asset name validation

[iLLiCiTiT]

Changes

• implemented asset name validation on each instance for publishing
  • asset name for publishing is used from collected instance from metadata which are handled only "On Create"
• workfile context is not used from "current context" (in api.Session) if workfile does not contain metadata
• changes from older Pype 2 PR that probably was not converted to Pype 3 (collecting of visible instances and group layers)

	Pype 2 PRs
pype	#1302

[iLLiCiTiT]

Waiting for proper testing and PR #1320 (added TVPaint schemas to project settings)

[iLLiCiTiT]

Not sure if validator should be optional? We discussed that we would want be able to publish into multiple assets which won't be possible with this validator.

EDITED: Question is beacuse of settings...

[mkolar]

I would make it non-optional by default. They can always change it in the settings.