Cleaned up MaterialPackageManager.edit_output_material().
Cleaned up MaterialPackageManager._get_output_material_editor().
Removing TempoInventoryManterialManager.
Cleaned up MaterialManagerWrangler._initializer_asset_manager().
Extended MaterialPackageManager._get_output_material_editor().
Removing TempoInventoryMaterialManager.
Merge pull request #370 from tiagoantao/master

Python 3: bug on unicode and New object classes
Implementing make_material_package_for_editable_mainline_class().

The method is being implemented on MaterialPackageWrangler.

The method will replace ...

    *MaterialPackageWrangler.make_managermade_material_package()

... as a way of making a material package for any mainline class with an
attribute manifest.
Implemented Selector.make_mainline_class_selector().