Graphite add-ons loader 3.0.0

New features

• Tree menu reflecting add-on directory tree
• Add management of facet_corners attribute

Breaking changes

• Add-ons are now found by .exe or .addon, addons that contains _addon in their names aren't found anymore
• Menu Externals is renamed Add-ons

Bug fixes

• Fix failed execution when no input model was expected for add-on