expose method to do gz.data3d.buffer coversion and get bake-able storageId

[ghost]

https://3d.io/docs/api/1/lightmap-baking.html talks about an thing that looks like this:

var storageId = '535e624259ee6b0200000484/bake/2017-10-20_15-22-15_lKCBcz/lighting.gz.data3d.buffer'

But there is no documented way to get this from the public API.

[ghost]

currently, the active model in the editor is cleaned up, converted into data3d buffer/json format, and zipped all in the frontend which results in the editor being un-usable on slower computers

i suggest we move that functionality to the backend

[ghost]

linked to #133