Allow subresource editing in AttributePropertyPlugin

[audse]

Current behavior

When you add a new attribute with the AttributePropertyPlugin, there is no way to edit or save that attribute.

Desired behavior

• Attributes should bring up a sub-inspector when clicked
• Attributes should have placeholder names and colors

Fallback option

I don't quite know how this will work, so if the above desired behavior is impossible, the following would be fine as well.

• Remove any option that isn't "load resource" from the editor
• Add a setting to enable/disable the AttributePropertyPlugin