Add entry_point attribute to Node and Group classes.

[mbercx]

Is your feature request related to a problem? Please describe

When I first wanted to obtain the entry point from a Group instance, I intuitively looked for the entry_point attribute. However, it seems that the entry point of a Group type can be obtained with the type_string attribute instead. Is there a difference between the type_string and the entry point? If not, perhaps we can add an alias for this attribute called entry_point?

For Node instances, I don't seem to find an attribute or method that directly returns the entry point. There is node_type and class_node_type, but they return something along the lines of '<entry point group>.<entry point>.<class name>' e.g. 'data.structure.StructureData.'. So, the user would have to understand this structure and adapt the output accordingly.

Describe your desired solution

I think it would be useful for users and developers if we can obtain the entry point for any object that has one with an entry_point attribute. Since users learn about entry points early on, it seems more intuitive to obtain a Node or Group's entry point via an attribute with the same name.

[chrisjsewell]

I agree 👍