Update graph features

[kevinl424]

Graph construction:;

• use PropertyGraphIndex
• SimpleLLMPathExtractor, ImplicitPathExtractor

Graph query:

• LLMSynonymRetriever (default now), VectorContextRetriever (neo4j supported vector search), TextToCypherRetriever

Fix streamlit app for adaption:

• https://docs.llamaindex.ai/en/latest/module_guides/indexing/lpg_index_guide/#using-the-property-graph-store-directly

[kingjulio8238]

@kevinl424 it would be cool to add capabilities for a parent retriever in this PR as well

[rawwerks]

+1 for using the new property graph from llamaindex

[kevinl424]

TODO:

• adapt response.metadata value of new property graph so that streamlit app can pull the specific nodes traversed
• no kg_rel_map key found