Fixes for API deprecation warnings when using plugin in Unity 6.4

[MaxPalmer-UH]

Fixes several warnings when importing the plugin in Unity 6.4

[rblenkinsopp]

The code changes all look good, have you checked that the .meta file changes increase in serializedVersion don't mean they have issues importing in older but still supported versions?

[MaxPalmer-UH]

The code changes all look good, have you checked that the .meta file changes increase in serializedVersion don't mean they have issues importing in older but still supported versions?

No, that's a good shout. There will likely be issues there.

[rblenkinsopp]

Looks good but check that serialised assets and it needs a changelog entry as well.

[MaxPalmer-UH]

Just checked importing the plugin in Unity 6.0, seemed to work fine and not show any warnings related to meta files or those components. Also added a changeling entry.