Resolve "Align all graph-related vocabulary in dantro with networkx"

This MR will align all graph-related vocabulary in dantro with networkx.

Using Graph, node, and edge now.

Can this MR be accepted?

• Implementation ready: Renaming
• Tests added or adjusted: Renaming
• Documentation extended or updated (no existing graph-related documentation yet)

• Code quality
  • Changes follow coding guidelines
  • Checked code coverage on new and adjusted code

• Ready for merging
  • Pipeline passes without warnings
  • History cleaned-up or squash option set
  • Changelog entry added
  • Version number bumped
  • Reviewed & approved by @herdeanu

Related issues

Closes #132 (closed)