Feature: Workfile Template Builder

[Thierry-Submarine]

I've based it on how the template builder works in Houdini and kept mostly the same logic

Few pointers:

• Placeholder Node uses a BurnIn node, I choose this one because it has both input and output support. After the actual Load has done the links (PEG, Composite) and position in the node view are copied from the placeholder node. Also BurnIn had a good attribute to store data, as this needs to be on the node as scenedata gets lost when using Harmony Templates as an intermediate to build your workfile template.
• Template path needs to be pointed to an unzipped .tpl folder, in my testing I grouped my nodes in the nodeview, made a harmony template from the group, opened the template, ungrouped and saved. This way the hierarchy is flat and as you would expect when you work on setting up your template

update: draft removed, tested and linting fixed