Remove `@version` in IPerson JavaDoc.
Refactor : Use IPerson attribute Map keySet .

Instead of moribund IPerson getAttributeNames() .
Eliminate IPerson method getAttributes() .

Use instead getAttributeMap().keySet() .
Also remove implementations of getAttributes().
Eliminate IPerson method getAttributeNames().

Use IPerson getAttributeMap().keySet() instead.
Remove IPerson setEntityIndentifier

Remove its implementations.
Trivial : Fix JavaDoc comment typo.
Merge pull request #460 from apetro/clean_up_iperson

UP-4289 Clean up IPerson.