Improve Choices Script and VN Text Box Layer

[CakeVR]

Adds the text_box property to the DialogicNode_ChoiceButton class. If set, the instance will set the text property on the text_box instead.

Adds exports to the VN Text Box Layer to allow turning off each individual override group category. Also differentiates between the Box Settings and the Box Animation Settings' subgroup.

[Jowan-Spooner]

Looks good to me, thanks!